For PotC:
There's always been an exit. Guests didn't have to go full back through queue, only a short way to the exit door. At least for guests initially entering the left side of the entrance. I think there's one on the right as well, but I've only seen guests escorted to the left side exit.
More recently, the PotC queue was reconfigured for FP. I imagine that's the new way out, as it would be very easy.
Quellman's post is solid. I think mostly it is the older rides that are trickier. Peter Pan comes to mind, but I haven't been on since the new queue.
If you chicken out on Astro Orbiter, you have to wait for next elevator ride down from the platform. Not sure about Buzz. that might have a way out other than queue, but it might not. It isn't scary though. I think to exit TTA, CM can let you access to down ramp- but you might have to wait. Again, that's not a ride most would exit.
If DD has any reservations about riding any Tomorrowland attractions, I suggest TTA first, though some parts are in the dark. Very dark, but very tame.
Once you enter the CoProgress, you are expected to stay for the full show. Trying to leave mid show causes big problems.
Energy is 45minutes. You can leave before you go on the ride, but once you are on it- I don't think there's any easy exit until it is over.
One more thing- only since we are on the subject- in many cases- attempting to leave the ride vehicle would be very dangerous. Someone was once killed trying to exit a Splash flue when it stopped (before I had lap restraints). The safari is also no exit.
The Nemo ride might be tricky to exit. Again not remotely scary.
Probably avoid Tough to Be A Bug and DINOSAUR.
Passporter has a great guide to address special needs/phobias. Also try the DISabilities area of this site. Guest services might also have handy guides available.