So here is my question:

I have a level whith multiple GameObjects each oh which has NetworkView attached. When I do RPC call to load the level for several players will all these NetworkViewed objects be in sync?

I mean whether Network.Instantiate is used to instantiate game objects whith NetworkView attached when level loads???

No. Only if you use Network.Instantiate the objects will know that they are the same instance and sync state.