I moved FSX Gold to Windows 11 several months ago in an attempt to resolve an API.DLL crash problem what started after some Windows 10 updates. Unfortunately, it didn't completely resolve the issue, but some steps I took lessened it.
Not everyone using FSX with Windows 10 or 11 has those issues and a potential remedy has been suggested. I haven't had enough time to test it, so can't say if it's a fix or not.
Anyway, I've had no issues different than updated Windows 10. Yes there are some things Windows 11 does that I don't like, but most I've been able to get around. I would suggest if you choose to update, download RUFUS and use that to upgrade. It allows you to bypass things such as force Windows logon, etc.