[arcticbull]

(IANAL) Once your I-485 is pending you can remain in the US for as long as it remains pending, on that basis. [1]

Most people also file an I-765 and I-131 alongside the I-140, I-485 and I-693 forms, and once approved, you'll be issued an EAD/AP combo card which entitles you to work in the US and return to the US on the basis of the pending I-485. This travel and employment eligibility is separate from any previous E-3 or TN status.

Once you file, you no longer have to maintain your previous nonimmigrant visa status, but if you don't, a rejected I-485 would subject you to immediate removal. If you do, you can return to your old status.

[1] https://citizenpath.com/faq/maintaining-status-after-filing-...