TN is non-immigration visa, be careful if you go

back and forth between USA and Canada ...

If your 485 is pending, you have to change to AOS (work with EAD and travel with AP). If you still use TN at the time, your GC case may be cancelled when you leave for Canada.

By the way, your 1st TN has to be issued by US port of entry, but you can renew TN year after year inside USA without leaving the country and re-entering. After you file 485, your further renewal may be rejected by INS then.