Apart from the appearance what is the difference between them? Is it a manner of how they mutate into them or is it just a locational term for them?

Trogs seem to be somewhat altered ghouls indeed. As is mentioned in The Pitt, the local monsters are mostly the result of radiation-caused mutation under the influence of all the industrial waste - and possibly some scientific kind of waste, too.
And the other thing - both are a reference to zombie flicks. In Romero's Land of the Dead, Pittsburgh is also a refuge to humans from a plague causing people to rise after their death, with the rich people living in one district with a tower as their haven and the poor folks in another, and all of them surrounded by a big electric fence. ^_^
Also, as in Land of the Dead, those ones seem to keep the knowledge of their former human lives somewhere inside their brains, where ghouls are the usual kind that slowly degenerates and has their brains rotten away slowly.