Massive G-Sync issues

Out of absolutely nowhere (after a Windows update possibly?), my newish computer started HATING G-Sync. I've used G-Sync since its infancy and have always loved it but now suddenly when it's on, I get horrific FPS, freezing, stuttering, the works. I've tried it across 2 PCs and 2 monitors. I've changed Game Mode settings, VRR settings, tried to do all the NVIDIA Control Panel tricks, V-Sync on/off here/there, and it all makes it worse at best.

All drivers of course updated for everything, only thing I haven't done yet is a BIOS update. Tried the DDU in the sidebar.

Turning off G-Sync and all VRR entirely ""fixes"" the issue but obviously it's not as good as before this all started. I bought a G-Sync monitor, I've always used it, I want it to function. ANY ideas what on Earth could be happening?

Most egregious examples I can think of is the likes of TW Attila and TW Troy will literally run at like 30FPS with G-Sync on. Troy's main menu will be 144 but the millisecond I move my mouse, the mouse is jumping and skipping and the frames topple to 40ish. Both do it in fullscreen and borderless.

I'm about to lose my entire mind.

Edit: a rule #2 benchmark won't mean anything because this is an intermittent issue and every time other than specified parameters, it's a perfect 144fps