Locked? unlocked? TT and 5th wheel RV's

We lock the door on out tt and did so when we had our class c as well. In fact, if I recall correctly, there was a sticker on the door of the c that said the door must remain locked and dead bolted while traveling.

As far as worrying about a first responder being able to get into your rig in the event of an emergency, that flimsy lock on your rig isn't going to stop them. Heck, almost every passenger vehicle out there automatically locks and they deal with locked vehicles all the time.