No, of course not. It also works without. All iPhone 12/13 models, AirPods (with wireless charging case) and AirPods Pro. And Apple Watch, of course, on the right side. So you don't need a MegSafe case.

If you mean the Sillikon/leather cases from Apple, no. From the iPhone 12 onwards, a magnet is built into the iPhone itself, the case is simply a situation; if someone wants a case and also wants to use Magsafe, for the Apple wallet or for charging.

The only thing you have to keep in mind is that it doesn't charge the device as quickly as when you have MagSafe.