From my time working at a shop with a decent sized walk-in, I can say that it is harder to control than expected. We had a good system that only sprayed when it was low, but occasionally it would spike up to 71-72% and it was hard to bring it down. This was usually when it was particularly humid outside, so just opening the door couldn't bring it down.
The one other feature it had, which benefited the customer, is that it would beep every 10 seconds whenever it was 71% or above. That way we were rushed to lower it if it did spike, since everybody was asking us what is wrong even if they had no idea what humidity it was supposed to have.
Temp was also tricky, but we ended up just buying a window unit and cutting a hole in the wall with the back sticking out into the back hallway
