What type of flying do you do most often? “Performance” can be a very broad category. Jetliner pilots have different requirements for what they want out of their sim than, say bush pilots or GA pilots, and so often require higher-end systems than others.
What sort of price range are you looking at? There is no point in anyone recommending a $500 GPU replacement if your budget is $250.
I have a 5800X3D on a B550 motherboard. There’s really no benefit to upgrading to another chipset with the Socket AM4 CPU’s. B550 is just fine. Now, if you were upgrading to AM5, that’s a whole other story.
I’ll bet you’re bumping into a GPU VRAM problem as well. The RX7600 only has 8GB, and I think you really need 12GB at minimum, and 16GB in reality.
I fly GA aircraft for the most part and I am getting about 40FPS. I understand that reducing the graphics quality will increase the FPS. The 5800X3D may be the way to go for me. I believe based on cost and performance, the CPU upgrade will the way for me to go.