Emperor: true, the smaller countries played the French vs Austrian camps against each other. they'll be concerned about an alliance between the two. but that doesn't mean they all automatically go into an anti French/Austrian coalition. you're still going to have a lot of them figuring (correctly, IMO) that F/A is going to win and work to remain on their good side. That goes for Bavaria. Karl was ambitious, but I'm in the camp that says he doesn't buck both France and Austria at the same time. Most of these countries only chose a side when forced to. they knew they were pawns of the great powers and in TL, the greatest land powers are France/Austria. Prussia was the best pound for pound, but they were simply outweighed massively.
the cause of the WOAS are quite basic: a bunch of countries thought they could dismantle Austria's holdings. especially after Prussia got the ball rolling with a victory. With two major powers backing Austria on land, it's questionable whether Frederick would have been so bold to begin with. OTL, he correctly saw that France, Spain and Bavaria would join in the partition of Austria, then backstabbed them when they did get involved. TL, he's in it for the duration and Prussia is front and center the entire war. France will be quite careful to keep the emphasis on backing Prussia off and beating Bavaria if they dare get involved. there will be no Italian front. Austrian Netherlands will only be a front if Prussia/allies make it a front to attack France. in such a scenario, the United Provinces aren't being threatened, so I find it hard to believe they'll push for it to be a front. While they don't like Austria being on France's side, they may very well say 'Silesia isn't on my doorstep, I'm staying out'. the WOAS was less about the succession and more about grabbing a piece of Austrian pie during a perceived weak moment. In this TL, you've got Prussia, which has some punching power, but is not a heavyweight, Bavaria, which is ambitious, but has no real power, a few lightweights, and Britain acting as banker. It's possible that everyone sits back and watches to see if Prussia can follow up Mollwitz with another victory, and then sees Austria win that war, which they will, if it's just the two of them. Diplomatically, Britain's main interest is breaking up the F/A friendship, not uniting them in war.