What Should I Check Before Moving an eSIM to a New Phone?

I’m replacing my phone and want to move my number from its current eSIM to the new device. The carrier’s help page says activation may require either an app or a QR code, but it doesn’t make clear whether the old profile should be removed first.

For people who have done this across different phone models or operating systems, what should I verify before starting? I’m especially unsure about carrier support, keeping access to the account during setup, and what happens if the new phone fails to activate on the first try.