Hmmmm I don´t know because there is no FPS counter in FS20.
It feels rather fluent in less populated areas with I guess 20 FPS, NY or other areas maybe 18 FPS, most settings on medium some important ones like texture quality, cloud quality, forest and vegetation quality on high or ultra.
Some add-on airports are impossible, there is 1 FPS while looking at the tower 
To be honest I had to save up all money to buy a Smart, VW Up or other super low fuel consumption car for my new nightly delivery job that´s why no flying with graphics card and 3D VR headset yet this is planned in early autumn.
But maybe not an RTX3090 this is way too expensive and would require a new PSU, a Radeon 6700 series, depending on the design of the graphics card, would be sufficient I think.