If you make alliance with Dorgania is this mean you will never be able to war agains them anymore? Is this will effect/remove some of the quest/side story?

I also have this question. If you side with The Dorganian King in the slavery bit of the game, does it lock you out of possibly conquering them? It might be too soon to ask this question. 

If so, I'd also like to question the relationship you'd be able to maintain with both queens.

Should you choose to conquer everything eventually