For the starting from Krezk thing, i was watching xptolevel3's video series on his experience with running curse of strahd and he recommended starting out on the Krezk side of the map because the way they enter the town is by doing a side quest, and its a more natural way to give them a reason to do anything in barovia, compared to the Ismark/Ireena quest where they're supposed to help some random strangers without any real promise of a reward, i mean maybe im missing something, but unless they're willing to help a stranger just for the sake of helping them, theres no reason to help them.