Head over to the Microsoft Flight Simulator forums. Update #3 has broken the performance of the sim. There are over 600 posts now about this issue. It's a very good chance it's not your video card. My system was running smoothly, no pauses, FPS drops, or stutters prior to the update. But now hundreds, maybe more, people are having the issue you are describing.
Problem after installing RX8600xt graphic card
in Microsoft Flight Simulator 2020 General Discussion
Posted
Head over to the Microsoft Flight Simulator forums. Update #3 has broken the performance of the sim. There are over 600 posts now about this issue. It's a very good chance it's not your video card. My system was running smoothly, no pauses, FPS drops, or stutters prior to the update. But now hundreds, maybe more, people are having the issue you are describing.
https://forums.flightsimulator.com/t/severe-performance-problem-in-1-14-5-0-identified-and-reported/376863/107