Не могу найти способ сделать красивый тултип pyqt5

То что вы хотите сделать - это показать всплывающий виджет без границ. Нарисовать это можно по-разному. Я покажу вам вариант, который мне нравится, но это не самый простой вариант.

import base64
from PyQt5.QtCore import Qt, QRectF, QSize, pyqtSignal, QTimer
from PyQt5.QtGui import QPixmap, QImage, QPainter, QPainterPath,\
    QColor
from PyQt5.QtWidgets import QWidget, QLabel, QHBoxLayout,\
    QGridLayout, QSpacerItem, QSizePolicy, QGraphicsDropShadowEffect,\
    QListWidget, QListWidgetItem


class NotificationIcon:
    Info, Success, Warning, Error, Close = range(5)
    Types = {
        Info: None,
        Success: None,
        Warning: None,
        Error: None,
        Close: None
    }

    @classmethod
    def init(cls):
        cls.Types[cls.Info] = QPixmap(QImage.fromData(base64.b64decode('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')))
        cls.Types[cls.Success] = QPixmap(QImage.fromData(base64.b64decode('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')))
        cls.Types[cls.Warning] = QPixmap(QImage.fromData(base64.b64decode('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')))
        cls.Types[cls.Error] = QPixmap(QImage.fromData(base64.b64decode('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')))
        cls.Types[cls.Close] = QPixmap(QImage.fromData(base64.b64decode(
            'iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAAeElEQVQ4T2NkoBAwUqifgboGzJy76AIjE3NCWmL0BWwumzV/qcH/f38XpCfHGcDkUVwAUsDw9+8GBmbmAHRDcMlheAGbQnwGYw0DZA1gp+JwFUgKZyDCDQGpwuIlrGGAHHAUGUCRFygKRIqjkeKERE6+oG5eIMcFAOqSchGwiKKAAAAAAElFTkSuQmCC')))

    @classmethod
    def icon(cls, ntype):
        return cls.Types.get(ntype)


class NotificationItem(QWidget):
    closed = pyqtSignal(QListWidgetItem)

    def __init__(self, title, message, item, *args, ntype=0, callback=None, **kwargs):
        super(NotificationItem, self).__init__(*args, **kwargs)
        self.item = item
        self.callback = callback
        layout = QHBoxLayout(self, spacing=0)
        layout.setContentsMargins(0, 0, 0, 0)
        # Фоновые элементы управления, используемые для поддержки эффектов анимации
        self.bgWidget = QWidget(self)  
        layout.addWidget(self.bgWidget)

        layout = QGridLayout(self.bgWidget)
        layout.setHorizontalSpacing(15)
        layout.setVerticalSpacing(10)

        # Значок слева от title
        layout.addWidget(
            QLabel(self, pixmap=NotificationIcon.icon(ntype)), 0, 0)

        # title
        self.labelTitle = QLabel(title, self)
        font = self.labelTitle.font()
        font.setBold(True)
        font.setPixelSize(22)
        self.labelTitle.setFont(font)

        # Кнопка закрытия
        self.labelClose = QLabel(
            self, cursor=Qt.PointingHandCursor, pixmap=NotificationIcon.icon(NotificationIcon.Close))

        # Содержание сообщения
        self.labelMessage = QLabel(
            message, self, cursor=Qt.PointingHandCursor, wordWrap=True, 
            alignment=Qt.AlignLeft | Qt.AlignTop
        )
        font = self.labelMessage.font()
        font.setPixelSize(20)
        self.labelMessage.setFont(font)
        self.labelMessage.adjustSize()

        layout.addWidget(self.labelTitle, 0, 1)
        layout.addItem(QSpacerItem(
            40, 20, QSizePolicy.Expanding, QSizePolicy.Minimum), 0, 2)
        layout.addWidget(self.labelClose, 0, 3)
        layout.addWidget(self.labelMessage, 1, 1, 1, 2)

        effect = QGraphicsDropShadowEffect(self)
        effect.setBlurRadius(12)
        effect.setColor(QColor(0, 0, 0, 25))
        effect.setOffset(0, 2)
        self.setGraphicsEffect(effect)
        self.adjustSize()

        # Автоматическое отключение через  5 секунд
        self._timer = QTimer(self, timeout=self.doClose)
        self._timer.setSingleShot(True)  
        self._timer.start(5000)

    def doClose(self):
        try:
            # Элемент мог быть удален из-за нажатия вручную
            self.closed.emit(self.item)
        except:
            pass

    def showAnimation(self, width):
        # Показать анимацию
        pass

    def closeAnimation(self):
        # Закрыть анимацию
        pass

    def mousePressEvent(self, event):
        super(NotificationItem, self).mousePressEvent(event)
        w = self.childAt(event.pos())
        if not w:
            return
        if w == self.labelClose:  # Щелкните значок закрытия
            # остановить таймер
            self._timer.stop()
            self.closed.emit(self.item)
        elif w == self.labelMessage and self.callback and callable(self.callback):
            # Щелкните содержание сообщения
            self._timer.stop()
            self.closed.emit(self.item)
            self.callback()  

    def paintEvent(self, event):
        # Закругленные углы и цвет фона
        super(NotificationItem, self).paintEvent(event)
        painter = QPainter(self)
        path = QPainterPath()
        path.addRoundedRect(QRectF(self.rect()), 6, 6)
        painter.fillPath(path, Qt.white)


class NotificationWindow(QListWidget):
    _instance = None

    def __init__(self, *args, **kwargs):
        super(NotificationWindow, self).__init__(*args, **kwargs)
        self.setSpacing(15)                                       
        self.setMinimumWidth(450)                                 
        self.setMaximumWidth(450)
        QApplication.instance().setQuitOnLastWindowClosed(True)
        self.setWindowFlags(self.windowFlags() | Qt.Tool |
                            Qt.FramelessWindowHint | Qt.WindowStaysOnTopHint)
        # Удалить границу окна
        self.setFrameShape(self.NoFrame)
        # Прозрачный фон
        self.viewport().setAutoFillBackground(False)
        self.setAttribute(Qt.WA_TranslucentBackground, True)
        # Убрать полосы прокрутки
        self.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
        self.setHorizontalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
        # Получить высоту и ширину экрана
        rect = QApplication.instance().desktop().availableGeometry(self)
        self.setMinimumHeight(rect.height())
        self.setMaximumHeight(rect.height())
        self.move(rect.width() - self.minimumWidth() - 18, 0)

    def removeItem(self, item):
        # Удалить item
        w = self.itemWidget(item)
        self.removeItemWidget(item)
        item = self.takeItem(self.indexFromItem(item).row())
        w.close()
        w.deleteLater()
        del item

    @classmethod
    def _createInstance(cls):
        # Создать экземпляр
        if not cls._instance:
            cls._instance = NotificationWindow()
            cls._instance.show()
            NotificationIcon.init()

    @classmethod
    def info(cls, title, message, callback=None):
        cls._createInstance()
        item = QListWidgetItem(cls._instance)
        w = NotificationItem(title, message, item, cls._instance,
                             ntype=NotificationIcon.Info, callback=callback)
        w.closed.connect(cls._instance.removeItem)
        item.setSizeHint(QSize(cls._instance.width() -
                               cls._instance.spacing(), w.height()))
        cls._instance.setItemWidget(item, w)

    @classmethod
    def success(cls, title, message, callback=None):
        cls._createInstance()
        item = QListWidgetItem(cls._instance)
        w = NotificationItem(title, message, item, cls._instance,
                             ntype=NotificationIcon.Success, callback=callback)
        w.closed.connect(cls._instance.removeItem)
        item.setSizeHint(QSize(cls._instance.width() -
                               cls._instance.spacing(), w.height()))
        cls._instance.setItemWidget(item, w)

    @classmethod
    def warning(cls, title, message, callback=None):
        cls._createInstance()
        item = QListWidgetItem(cls._instance)
        w = NotificationItem(title, message, item, cls._instance,
                             ntype=NotificationIcon.Warning, callback=callback)
        w.closed.connect(cls._instance.removeItem)
        item.setSizeHint(QSize(cls._instance.width() -
                               cls._instance.spacing(), w.height()))
        cls._instance.setItemWidget(item, w)

    @classmethod
    def error(cls, title, message, callback=None):
        cls._createInstance()
        item = QListWidgetItem(cls._instance)
        w = NotificationItem(title, message, item,
                             ntype=NotificationIcon.Error, callback=callback)
        w.closed.connect(cls._instance.removeItem)
        width = cls._instance.width() - cls._instance.spacing()
        item.setSizeHint(QSize(width, w.height()))
        cls._instance.setItemWidget(item, w)


if __name__ == '__main__':
    import sys
    import cgitb
    sys.excepthook = cgitb.Hook(1, None, 5, sys.stderr, 'text')
    from PyQt5.QtWidgets import QApplication, QPushButton
    app = QApplication(sys.argv)
    w = QWidget()
    layout = QHBoxLayout(w)

    def callback():
        pass

    layout.addWidget(QPushButton(
        'Info', w, 
        clicked=lambda: NotificationWindow.info(
            'Info', 'Это сообщение будет закрыто автоматически', callback=callback)))
    layout.addWidget(QPushButton(
        'Success', w, 
        clicked=lambda: NotificationWindow.success(
            'Success', 'Если вы знаете какие то решения, буду крайне признателен!', callback=callback)))
    layout.addWidget(QPushButton(
        'Warning', w, clicked=lambda: NotificationWindow.warning(
            'Warning',
            'Щелкните содержание сообщения!',
            callback=callback)))
    layout.addWidget(QPushButton(
        'Error', w, clicked=lambda: NotificationWindow.error(
            'Error',
            '''
<html>
<head><head/>
<body>
  <p>
    <span style="font-style: italic; color: teal; font-size: 25px;">
      Не могу найти способ сделать красивый тултип PyQt5
    </span>
  </p>
</body>
</html>
            ''',
            callback=callback)))
    w.show()
    sys.exit(app.exec_())