Technically, your question is confusing; you asked about Replicated Actor, so by default, if an actor is replicated, the visual “art stuff” like meshes, materials, and textures are not replicated over the network. These assets are assumed to already exist in the clients’ game’s content, not dynamically sent over the network. So you don’t need to spawn an actor on the client and server, then the system will do it by default
If you spawn an actor on the server side, it will handle the movement and collision for you, but don’t forget to enable Replicate Movement on the projectile actor