Hi,
Indeed, it's a stuggle to give a consise explanation of photon, playmaker and the concepts in generals. So you need to really keep up and study it over and over again, reading as much as you can from various sources until it starts to mentaly make sense, and YES, doing your own version and implementations is the best way to gain experience, so this is good you are getting down with making your own simple tests.
items/players is the same really, it's a gameObject you instantiate over the network. So if your player is for example creating a sphere, the sphere gameObject must obey the same rules as the player prefab, that is it has to have a photonView component at the very least so that all players see that sphere.
then if the sphere has to implement features, add a fsm to it and start adding feature using the same patterns as the player prefab ( that is if it has to behave in certain way, only the "is mine" version of the sphere should implement actions, and all the "is not mine" sphere should simply catch up with it.
Does that make sense? the player prefab is nothing special in it implementation over the network, it can be anything really.
bye,
Jean