If I fly in an altitude restricted zone, say 150ft for arguments sake, and I have a RTH altitude of 200ft set how will the drone behave when I press RTH?
The best thing to do would be to run your own experiments. Just make sure that you are always within radio range with your controller so that you can cancel RTH and take control if things don't go as expected.
In this situation the best solution would be to ensure your RTH height is configured to less than 150ft, as that will always allow the drone to come back
under that altitude restricted zone.
But, if your RTH is configured to 200ft, my guess is that there are two scenarios.
One, you're currently flying safely
under the altitude restricted zone. If you press RTH, the drone will first try to climb to its configured 200ft RTH height, but will bump into the 150ft ceiling restriction and be stopped from climbing any higher. What happens then? I don't know. But you can cancel RTH and resume control.
Two, you're flying somewhere outside of and
beyond the altitude restricted zone. Press RTH and the drone will first climb to its configured 200ft RTH height, then turn for Home. When it bumps into the outer edge of the 150ft altitude restricted zone it will stop and be prevented from entering the altitude restricted zone. If you still have control signal, you can either cancel RTH and/or simply decrease throttle to descend to less than 150ft to allow the drone to safely traverse
under the altitude restricted zone.
It's similar to other GEO zones. If you fly your drone around to the backside of a GEO zone, and then lose the control signal, the drone will go into RTH mode and fly a straight direct line back Home. If that straight line intersects a GEO zone boundary, it's like running into a brick wall. It'll stop. If you regain control signal that gives you options to navigate back around the perimeter of the zone. But I suspect if you have no control signal the drone will just sit there until low battery forces it to land.