Can I use this flight controller?
Matek G474-HELI RC Heli Flybarless Flight Controller
I want to do either a 3 motor tilt or a 4 motor vtol fixed wing
No, this flight controller does not have enough flash memory to run ArduPlane.
OK thank. What about the Frsky R9 Pilot?
Why that one? It’s supported but there has been no mention of those on the forum. Wondering where you are coming up with these choices. YouTube?
I Thought I had seen it here and it seems useful having the integral r9 rx’ Anyway I’ve now ordered mtek h743 wing v3
That is a very good choice 
Do you think this controller could also work with a trad flybarred Heli to aid learning to fly? It’s a trex 500
You will find most versions of the Matek H743 board being used for Heli.
Does it work with a trex 500 flybarred? With or without tail gyro?
Post in the Trade Heli thread but I think all standard Heli configurations are supported.