Sounds like you have a similar build to me.
I have the monitors set at 4K, NVIDIA and MSFS at 4k too. I adjusted the NVIDIA and MSFS graphics settings as per another post on optimising 4K performance and for me overall, I have a good smooth flying experience.
These setting adjustments were against a RTX2070 but were a good starting point for me. I’m not one of the “must have 60FPS” junkies as I realise that a game of this complexity is never going to achieve that consistently at 4K with todays hardware.
Maybe in the new year I’ll update my motherboard/CPU to one with PCIe4 as I’m sure that will improve performance slightly.
There are lots of posts here reporting people with good graphics cards find they’re limited by CPU single thread and there’s currently a battle between AMD and Intel over who has the best single performance.
Having a CPU with good multithread performance is important but single thread performance is critical for the way MSFS works.
Intel are due to release a new CPU Q1 2021 and from the reports I’ve read, they’re suggesting it will beat the latest AMD CPUs in terms of single thread performance. Time will tell.
I’ll wait to see how the benchmarks turn out before deciding whether to swing in the Intel or AMD direction.