I had serious problems with my rig as well. i7 9700, RTX 2070 SUPER, 32 GB and still MSFS2020 had a lot of stutters and very low frame rates. In fact frame rates kept decreasing while flying or even when siting on the apron. It looked like I had a memory leak or something else seriously wrong. I tried every advice I could find in this forum, updated drivers, used different Windows 10 versions, but nothing helped. When I ran a benchmark test on my rig, I found that both CPU and GPU were running far below what I should expect. Then I tried the program Ccleaner. It found a lot of broken or wrongly referenced files on my system and performed a cleaning. When I ran a benchmark after that, my system suddenly was top of the bill. And MSFS2020 now is running so smoothly. With high/ultra settings I now have excellent frame rates (typically 50 fps) and stutters are gone. Visuals now are beautiful.
Of course, I do not know if this is going to solve your problem, but you can download a trial version of Ccleaner and check whether it helps. Again for me it did, and I bought the program right after that.
Good luck.