once your I-140 is approved, you should immediately submit an I-485, an EAD and AP applications. Your file will be recalled from NVC to a TSC or another service center for AOS. NVC will send you a letter requesting if you want to continue with consular processing, to which you will answer "no, i have done AOS". The reason you want to wait until your I-140 is approved before submitting I-485 is that if your I-140 is denied and you have already submitted I-485, then you are stuck with no green card and no ability to get a TN again. Look carefully at my signature to see what i did. Notice that i was issued a new TN status while I had a approved self petitioned I-140 in hand, though i had not submitted I-485This is a self petition.
What would happen if I submit the I-485 after my I-140 NIW is approved?
Self-petition or not, I-140 irs not in itself grounds for TN denial, and there is no need to go consular route. File I-485 as soon as ypur TN is appoved, along with AP and EAD, and you will be free a nd clear of TN within months.
Consular will take several months.
You should wait until your I-140 is approved until your file I-485. The reason to wait is because there is a real possibility your I-140 will be denied. If it is denied AND you had filed I-485, then your TN status is dead and you are not able to restart the TN status. Perhaps Nelson didn't notice that your are filing a EB2 National Interest Waiver petition, which can easily be denied. There is little chance that EB2 NIW based I-485 applications will go into retrogression soon, so there is no need to think about concurrent filing regarding quotas.Wouldn't be better to wait until the I-140 is approved? As far as I understand this is the safest route.
The reason for selection CP on the I-140 form is in case of a disaster when trying to re-enter with a TN and pending I-140. Let's say you were trying to re-enter under these circumstances and the CBP official refused you entry, claiming that you had demonstrated immigrant intent with your I-140. The chance is small, but it could happen (and the officer would be wrong), and there is little you can do about. You would be stranded in Canada and unable to file a I-485. But as you had selected CP on your I-140, then when your I-140 was approved you could be processed at the US consulate in Montreal. Just a little backup plan is case of worst case scenario.One should apply, as you say, for AOS. Why dance around?