you are worrying over something that isn't an issue.
whether he changes his address with CIC for his application has nothing to do with his entry into canada and is not your issue. one thing has nothing to do with the other. CBSA isn't going to know he changed his address with CIC and they aren't going to care. if they find out by some miracle, then all he has to say is, he is planning to visit you while the application processes and wants to be sure he doesn't miss any letters from CIC. it's not even going to come up, because CBSA isn't going to care about the details of his application. All CBSA cares about is if he is following the rules. The fact he has submitted a PR application shows them he is.
he is going to be asked the standard questions everyone else is asked. if he gives the primary officer a reason for him to need further investigation, he will be sent into secondary. all he has to say when entering is "i'm here to visit my wife. my application for PR is submitted." generally he's not going to be sent into secondary unless he sounds or looks like he's doing something wrong. visiting his wife while his application processes is not wrong. leaving your apt behind and trying to enter canada with all your worldly posessions is probably going to be suspicious.
your issue is whether he looks and acts like a visitor or acts like someone who is moving before they are allowed to. since he's visiting, he should be able to maintain some ties to the us when visiting canada, no? what was he planning to do with his apartment and belongings? when someone goes on a trip, they typically don't give up their apt and belongings, right? just because he wants to stay for longer, doesn't mean the same doesn't apply. yes, if he gave that up and tried to cross the border with all his belongings, that would probably lead to an issue. that's not visiting, that is moving. so, he can certainly keep his stuff in tennessee, come visit you, get approved, then go back to "pack up".
unless he gives CBSA a reason to be suspicious, a majority of people breeze through the border. he needs to be prepared. that is all. being prepared means being able to show ties to the us, proof of his application and knowing not to say "moving" or "living", and not showing up with all his belongings. if he plans to give up his apartment while he's visiting you, it's best for him to do that after he's already gotten to canada. it's not recommended to get rid of anything before being approved as pr. there is no reason he can't visit, unless the "all or nothing" scenario suggested is financially motivated.
be prepared, know what to say and act as a visitor. there is absolutely no issue and a very slim to no chance he will face issue at the border.
