Just got my Air as well and it looks lovely - I am just waiting for my ordered case to arrive before migrating from my XR.
By the way, a question: should I migrate the SIM cards before transferring the whole content from my old phone, or vice-versa?
here is what i did, and it went ok. note this assumes you have iCloud storage plan turned on.
1 do a final Cloud backup initiated on yr old phone.
2 sign out of iMessage and Facetime on your old device
3 remove your old device from Find My on yr old device
4 start the simple process that apple outlines (with two devices overlapped). transfer everything either via wi-fi or by bluetooth. either way works. but give yourself up to 30 minutes for the transfer if you have a lot of data.
5 after the transfer of data from the old to the new device is compete, the new device will show its all happy and wanting to do the final steps to finish the new phone setup. do that.
6 its during that step that you will be able to transfer your (e)sim to the new iPhone. some carriers have a quick transfer, other carriers need to send you a text message with a link for a QR code. either way isn't usually a problem.
as per yr question, i was really confused about the timing for this. i planned ahead and actually changed my physical sim to an esim on my old device in order to make it easier to go from esim to esim. but i think it doesn't make it any easier in the end. however, read and re-read what your carrier says to do about transferring to an esim. and, anyway, this is the point when its done.
7 after you have completed the esim setup completely on yr new device, make sure its working. call yr new device from somebody else's phone, and see if it rings. whatever you do, try not to delete yr esim on yr new device. some carriers charge a fee for giving you another QR code to activate it a second time.
if your new device can give/get calls, then any later problems you have will not be carrier related. if there are problems it would be apple related.
8 on the old device, check under Cellular to ensure that no esim is still active. just delete it if you need to. its important to do this. apple has reported the iOS 26 needs this step to be sure to not have iMessage problems later.
9 if you are trading in or giving or selling your old phone to someone/somewhere else, go back to the old phone and initiate the well outlined steps to wipe your phone. its safest to do this anyway. select any and all options it gives to do a thorough and complete wipe. it takes around 5 minutes for it to complete.
10 after that, on your new iPhone, sign in to FaceTime and iMessage. Then sign in to Find My.
