I don't own the game, but at first glance seems some kind of bug may have been introduced after beta? No doubt you considered that.
More generally, you have a great rig and the 200/300fps are great and to be expected with your kit.
Of course it should be at least as good now.
The only thing I find odd (not saying this is your fault) is that you are getting a CPU bottleneck. That's really weird. Your CPU shouldn't bottleneck anything even with an RTX 5090.
Could be a game bug - if others report the same, that's your answer and a patch should be forth coming.
Regardless of that, if me, I would go over my PC settings. Run a DXDIAG check. Run Performance Monitor 1 minute diagnostic test, and then the one minute performance test. They are defaulted to one minute and may help. Additionally your GPU software. Any change in driver?
It's really hard to pin these things down sometimes except for the person (you) who is using the PC.
A bit of troubleshooting, of your choice, plus finding out if this problem has been reported else where should help.
Beyond that, good luck. I can imagine your frustration experiencing this with state of the art (expensive) kit.
One thing for sure though. It will be patched. You will find out why (some obscure setting, whatever) or, seriously, when you put your PC on next day or sometime the problem will be gone. That's happened to me in the past, but usually not that simple.
Good luck, and please post back if you find the cause. (It may just, "clear up," by itself if you are very lucky.?) !
P.S. You mentioned it's only that game. That's a good start. Coming out of Beta in game, or even NV software settings may need changing. You could also after checking in game settings, limit frame rate to 120fps, and set refresh to "application controlled." if using NVCP.
Most games can be left at highest possible for refresh. But a few don't like that one bit. WRC 8, & 9 either need to control the refresh rate. For some reason the refresh needs to be the same as fps max setting or an exact fraction of it. Not likely with your game though.
Anyway, maybe something there will inspire a thought? Again good luck.
