I continued with the main quest line, and was asked to hold a peace council with the Imperials and Stormcloaks. This made me wonder what would have happened if I had completed certain quests before the main quest line:

Would Arngeir agree to hold the meeting if I had killed Paarthurnax? What happens if he doesn't?
What happens if I had completed the Imperials/Stormcloaks questline prior to holding the council?
How do my decisions to hand over Markath to Ulfric in exchange for Winterhold and the Pale affect the game?

This is all really confusing to me, so if someone can answer one or all of these, that would be cool.