I just got my iPhone 11 Pro Max and giving the wife my XS Max phone. She has an iPhone 7 Plus currently. Will I need to move her SIM card to the XS Max, and if I do...will it still do a phone to phone setup?
You should backup her 7 Plus to iCloud, then reset your XS Max to factory settings, then input her old SIM into your XS Max, then finally have her log into your factory reset XS Max with her account and restore from her latest iCloud backup.