Personally, I'd like to see the categories split, outright.
IGT and RTA.
IGT would favor those who want to play in realtime for each mission, regardless of hardware but I also understand it would cause alot of tie-breakers with how the game only counts to the second. This wouldnt be strictly limited 1x speed only. Rather I'd like for it to be a showcase of who has the best solutions for each mission.
RTA would stay as is, whether the ingame speed is restricted or not. Maybe down the road, an FPS cap or some kind of limit can be imposed.