PUN Classic is PUN 1.x and not recommended anymore. PUN 2 fixed a lot of the problems and is still something you can use, yes. However, there are not a lot of reasons, why you shouldn't use Fusion. It supports newer features of Unity, has proper authority (which clarifies who does what) and the synchronization of objects is better out of the box. Not everything you do with it has to be high-end. Having advanced features doesn't mean you have to use them. But later on, you could. Coming from PUN, use the shared mode and you don't have to worry about how the host runs everyone's state via input alone.