What happens to Siths when they die ie can they become force ghosts or ?
Some jedis Have turned into force ghosts what happens to the Sith/Sith lords when they die can they become force ghosts as well or something similar but more sinister?
Wow awesome thats pretty cool. Sorry excuse my ignorance when they go to the netherrealm of the force are they limited to what they can do ie restricted compared to jedi force ghosts etc?
Also the spirits that remained trapped in objects (ie DARTH Andeddu etc) are they also restricted or limited in what they can do and can they influence others or interact with them ?
They're about as limited as anyone can be. They can't interact with the living world, and are, in a way, dead.
If they do the object thing, they can talk to others. I remember Exar Kun used Dark Side Tendrils on Luke, so they maybe are able to interact a little bit. But what they can do is still pretty limited, especially by location.