The 4090 is fantastic. I do fly in VR sometimes so it really shows it’s strength there, but in flat screen mode, it’s great too. I rarely see GPU usage get above 70% in all scenarios and this is with Frame generation enabled.
The 7950x3D is an absolute beast. With AI traffic disabled, Vatsim enabled (FSLTL & Justflight) at a moderately busy airport in a big city (EGLL), with the ultra preset in the Fenix, I’m getting around 80 FPS on the ground while taxiing, and upwards of 90 in the PMDG.
Just make sure to update your BIOS and Drivers and everything should work well. I disabled hyper threading (SMT) but not actually sure if it makes any difference.