BGRAControls it's slow (I'm sorry).
1) Yes, as I explained BGRAVirtualScreen is just a TPanel, can cover all controls if placed over all of them. (not need to use all bgracontrols, it can use LCL controls as well).
2) Tested in Linux and Windows. But in macOS it gives a black Window. And also an interesting effect using Qt, it makes yellow garbage (mixing different parts of the screen due of how LCL works capturing...) (I find this interesting since I'm also an artist).