OK, I did test the proper “core parking” with Game Mode + Game Bar + Prefer cores Auto in BIOS. It does work, but it doesn’t cure the stutters. Then I added Process Lasso + it’s ParkControl app to the equation. I didn’t see any significant change. So I went back to BIOS “prefer frequency” + Game Mode off + Game Bar off + Process Lasso setting everything to CCD1 and MSFS to CCD0. It basically performs the same, with no change in stutters. It may give a bit better performance but I have so much overhead it doesn’t matter. Stutters are still there though. It looks like all of that doesn’t matter, along with most MSFS settings. Maybe high LOD and Ultra clouds just may make stutters more frequent, but other than that - same thing, no noticeable effect. I gues I’ll have to get used to it until hopefully there is a fix. Everyone is advised to vote for this bug report so it gets noticed.
It is ridiculous that many people can’t get a completely smooth performance with ultra-high-end systems. It was all about FPS with all other games, which hardware could help with, but here - we have plenty of FPS but it doesn’t help.