If you’re building this system purely for MSFS, don’t go with the 10900K or 5900/5950.
These are CPU’s built for productivity tasks.
There is currently no game or sim that will utilize all the cores / threads these CPU’s bring. It’s a complete waste of money.
Grab a 5600X or 5800X. CPU’s with more cores are simply a waste.
To give context: I have a 5800X myself, and even that processor is normally showing around 15% total use outside of photogrammetry areas. A bit higher within.
A 5950% will most likely be idling at under 8% load, with one thread (that runs the main tread) close to maximum. Complete waste.
If you’re also going to be video editing/rendering/3D modeling on the system, then those CPU’s start to make sense.