Small correction to what I've said ealier, some TTX+ cabs used 7600 gs instead of AMD cards so most likely not an issue with AMD shenanigans.
About running the game natively (as in, launching game directly through game.exe), you could in theory use JConfig, although when the game is run through it, it doesn't set the window to 1360x768 and many 2d elements render as if it was actual resolution when running in Pro Mode (called High resolution there). It's in attachments if you want to try it (High resolution setting sets Professional mode in BG4 Tuned, I think it also only works with BG4 Tuned, not sure)
Additionally, on 2.73, when using DX12 and forcing resolution to something other than 1360x768, the game actually starts to render 3D in that resolution instead of staying at 800x600 (still no minimap however)