Welcome back! That was before my time, but it's cool to see more of the old rFactor guys come out of the woodwork. Be sure to check out or discord, that's where most of the chatter is these days. There is usually some one around who will run with you on the server.
It might be worth while taking some sort of survey of the regular players to see what their specs are and what frame rate they get. Maybe then we could get a better idea of what it takes to currently run the game well beyond the vague "decent gaming PC".
Easiest way to race with other people is to join the official UHL server 'www.uhlhydroplanes.com'. I believe there is a way to set up your own server but it's a hassle and above my skill level.