Can i use grabWidget() and paint widgets to QWidget, using information from the QRect() of other widgets? If yes, how?
Yes, of course you can do that, and you'll get a QWidget with pictures of other widgets in it. They aren't QWidgets, so your users won't be able to interact with them. Why on earth would you want to do something like that?

I suspect that you are not correctly designing your layouts, which is why you are trying to reinvent the wheel.