back up

When you back up each iPhone to your Mac, it will create a separate backup of each device’s data. The backup of both devices will be labeled by the name of each iPhone on your Mac. Just make sure they have different names for ease of maintaining backups.

To backup: https://support.apple.com/guide/iphone/back-up-iphone-iph3ecf67d29/ios

Use set up as new device. That will connect it to your Mac. If you prefer, make a iCloud backup first (just in case). Settings > {Your Name} > iCloud > iCloud backup. Once complete. connect it again to your Mac.

Yes.