I have a very mid range system I7-9700 and a gtx 1660ti. I can get 30-35 fps easy on high end no issue depending on the city (I currently have it capped at 30 fps though for smoothness). This is a problem with your system and not FBW. Though they are going to be optimizing everything more as time goes by.
Systems wise, the A320 is the best airliner available for me as I am not interested the CRJ. I have downloaded the experimental version of FBW with the better autopilot and FPM and have had no game breaking issues and have gotten rid of the flyback bug. Keep up the great work FBW!
If you love the 747 so much, download the Captain Sim 777 which relies heavily on the default Jumbo’s avionics. I believe there is a salty sim compatibility mod on flightsim.to and an eicas mod to get the 777 engine gauges to look a little more believable as well.