I play MS FS 2020 on an i9 9900K (no OC), an RTX 2080 Super OC Edition, and 32 GB 3600MHz CL17 RAM, and I have a 120 Mbit (15 Mb/s) internet connection (download).
I play on the graphics setting "High End", the step below "Ultra", and I use a 2560x1440 monitor.
EDIT : Peak system memory usage has been 26 GB and 7.7 GB VRAM
I originally had the game installed on a 2.5" SATA3 SSD, but I quickly moved the game to one of my NVMe drives, because the game has some quite significant load times.
And even with the game on an SATA3 SSD, I experienced brief performance drops when flying in extremely dense scenery - it seems to have improved with the game on my NVMe drive, and I must admit this is the first game I've tried, that actually appears to benefit from being on a fast NVMe drive (in certain scenarios).
The only change I have made to the "High End" graphics settings, is that I have maxed out ground vehicles, air traffic and sea traffic.
In a very big city with dense scenery I see anything from 34 to 40-ish FPS, sometimes spikes into 50-ish FPS. 40 FPS seems to be the average in big cities, but it does go below as mentioned.
At high altitude, or over water, my setup maxes out at 62 FPS.
The average FPS on my system, seemes to be between 40-50 FPS, depending on the weather and time of day.