The grip will fit any bare phone unless it is less than 58mm wide. It even fits the iPhone 12 mini, which is 62.4mm wide for reference. When sticking to cases, the general rule is the case can't be silicone or heavily textured, otherwise the adhesive will not stick.
Snap 4 Luxe is Apple MagSafe compatible, adhesive assisted. It's more difficult to remove than typical MagSafe accessories because you can use other MagSafe accessories on top of it and we don't want it coming off! The magnets inside your iPhone just aren't strong enough to keep Snap 4 on your phone if you stick it to a fridge or car mount.