MMO Realtime shooter TopDown

Hi i want to make an top down mmo shoter at least demo for start but i duno really about performance shoud game like this use bulet caracter colision or simple raycasts whit some visual effects ?

If it is a MMO: none of those. This is highly discussionable and subjective question: sometimes it is okay to trade performance there for features somewhere else. The best bet will be opening a discussion on the forums instead.

You should check how MMOs of current generation achieve gameplay vs computation costs balance like EVE Online, Haven&Hearth and so on.