I haven't gotten that far yet but do any IA quests cross over into ToB ? or are there distinctive quests for each section? I don't want to cross over and miss out on a quest that did not develop in time. Does watchers keep interact with other areas?

If you go to TOB before completing an SOA quest, you can't continue that quest in TOB (because you will lose access to SOA areas and some possible other reasons).

One of the mage stronghold quests has an extension which will trigger in TOB, but again, you have to had completed the SOA portion of the quest while you are still playing the SOA portion of the game.



This question is too general to have a negative answer.

Yes, depending on various factors, WK may interact with other areas.