I was wondering what changes can occur during the season unending quest. For example, what changes occur if the Stormcloaks have just taken Whiterun and Markarth, or the Empire is in the quest before taking Windhelm.

Biggest change? Different guard uniforms.

Other than that, not much changes besides perhaps some quests bugging...

I meant what changes DURING the peace treaty. Surely a conference where the Stormcloaks are just about to attack Solitude is different than a conference where the Stormcloaks have just taken Whiterun.

Now that I don't know. I've never done any of the civil war quests.