Thought I could just install Win 10 from a bootable USB like on a normal PC but if I get a new GPU I won't be able to boot into windows (no EFI and no Start-Disc Manager from bootcamp) or am I crazy ? ? ?
I'm a proponent of having boot screens, so I'd either get a flashable card, or pay to flash one, or keep a secondary card in the computer that has Mac EFI, or at an absolute bare minimum keep an EFI card in the closet as a backup in case you need it.
But I've seen people here without Mac EFI who have installed Windows somehow. Maybe the Windows installer inits the GPU? Hopefully one of them can chip in.