Could anyone tell me how the war is supposed to play out

I've primarily played Russia and the Ottomans, though I've tried most of the viable nations at one time or another. There are certain trends in the flow of aggression in the game. Early on Prussia and Sweden, Austria and the Ottomans, Russia invited into the Coalition against France with Great Britain, France conquering Portugal and Sicily. Sooner or later France will get into conflict with Prussia or Russia (and Prussia usually has no chance).

I've been enjoying it more as a sandbox game, trying to anticipate the usual AI moves and counter them somehow. For example, the Ottomans will often go after Egypt and GB after Tripolitania to liberate and puppet Cyrenaica. As Russia, I've been trying to get ahead of these moves and end up with control of both.

Also, while it's smart to assault a target when they're involved elsewhere (Russia attacking the Ottomans when the Sultan is dealing with Austria) I've lately been avoiding that tactic as too 'gamey' and trying to deal with countries one on one. It's been more challenging to me this way.

There have been times I've had the option to form a coalition against France (as Russia, Prussia and Sweden). Getting one formed when I've already been in conflict with my potential allies is something I've not been too successful with - mostly because I tend to play the military part of the game and let the politics and economics part slide.

Yes, Portugal and Sicily do have their doom awaiting. (I tried Sicily as my first country when I first got the game.) You really can't play a neutral game in hopes of grabbing small targets while building up your country as France is far too aggressive.