>I am just confused since some people say that I need to install Windows 11 on it to be able to play some titles, and others say that I dont!

The Steam Deck runs an Arch-based Operating System called SteamOS. Most PC games that run on Windows cannot run natively on SteamOS. Instead, they have to be run using a compatible layer called Proton. Proton does a good job making a lot of PC games runnable on the Steam Deck, but it's not perfect. Not all games on Windows will run on Steam Deck even with Proton. You do have the option of installing windows, but I don't recommend doing so. The best thing to do is make a list of all the games you want to play on the Steam deck and research their compatibility before you decide to get a steam deck. That, or just get a PC with Windows.