Since Tvheadend and oscam are used together but don't need to be on the same system would there be and ad/disadvantages in having them on seperate systems?
No problems, work fine on separate systems.
But does it help take the load off Tvheadend if oscam is on a different system or does it provide an additional overhead?
Oscam usage is to small unless if you have BIG sever or cacheex ...etc.