If you have movement at the corner, you have no choice but to caulk. Around the base, there is the potential for movement so again, caulk is called for. As for a place for water to weep, it can do that at the grout joints just above the caulk.
When I redid my shower, I used lots of deck screws to lock the framing at the corner to prevent movement. I also used the heavy fibreglass mesh tape on the modified mortar joint of the concrete backer and the corner got a double layer of KERDI where it overlapped at the corner. The tiles met evenly at the corner rather than one tile going behind the other. I grouted the corner and there has been no movement what so ever.