PID is more than enough to keep level. FPV relies on manual flight, but you can get Ardupilot for autonomous missions. There's no need for RL, nothing to gain here; level flight and following waypoints is a solved issue already.

And frankly as a pilot, I'd rather not see any completely autonomous drones with no oversight in the sky - that's one incident away in which blame cannot be put solely on the operator from getting the hobby completely banned.