I’ve just been through an upgrade myself, using this thread and other to try and tie down some decent performance. Base is 5800x3d, 4090 all water cooled.
In the end I did a fresh install of Win 11, and MSFS but the only, only way I can get decent performance is with Rivatuner , set to either 30 or 45 fps, and even then when it’s in focus , ie active on screen. Given this, it’s clearly a tuning issue. I struggle to understand why Rivertuner can make such a difference. What’s it doing that we can’t replicate in other ways.