I ordered a 12 (trading in my XR) from Verizon. The phone came with a SIM card installed. I backed up my XR to iCloud and then restored the 12 from that backup. Left the XR sim in the XR.
All good regarding the XR backup to the 12 in general.
However, the activation of the new phone was a nightmare. During the normal iPhone setup on the 12 (choose language, input your wifi, restore from backup, etc), it went to a screen for activation that said something like “next” (the usual). Well, I got an error message. Then it gave me a phone number to call to activate. I called it and it was some crazy automated message about making a collect call. The hell?
Then I called the normal Verizon contact number and went through the prompts to activate the phone. I had no idea if it would work and by the time I saw the cellular bars show up in the status bar (meaning it was activated), the phone was nearly done restoring from the XR backup.
So, yay, it was fully restored and activated. Then I started to receive texts from Verizon and notifications from the Verizon app saying I had run out of data (I’m on the small 2GB plan, don’t need unlimited). So I had to call again and talk to a real person about the data issue. They fixed it for me, but damn, what a process.
This is only my experience, though. I hope it goes smoothly for you!
Edit: Please note that I didn’t do any “Quick Setup.” I prefer to do the standard Apple method (sans having the old phone directly communicate with the new phone for transferring content… better said “the old way”). Hopefully the method you use works great.