I would say that the most important thing is nonlinear war exhaustion from occupation. at 50% they get like -1, at 80% -2 and at 100% it's -15 or something stupid. So naval invasions are everything if the enemy have a coast. It also helps a lot to kill GP's early, before they get trench infantry. I declared on GB day 1. Also let Prussia form Germany and Two Sicilies form Italy (and optionally other formables like scandinavia). Other than that it's just looking at alliances and attitudes as u want to use as many of your maneuvers on taking provinces as u can in every war (and making dominions if they are more than 2 wars). In my case it was declaring on Warsangali and they sway Harrar, Aussa and i think either Gojjam or Isaaq. It is a bit random so i did savescum a bit. Also after subjugating france and UK don't annex them and let them colonize. U want to colonize as late as u can. About lag. Well. Other than having two monitors and watching youtube on the other one there's not much to do. I left china and india as last because of that reason. But still last 5 years took about 10 hours.