Always go Influence when in Western Europe these days - it's simply amazing. That and Religious used to be my opening gambit with Defensive/Quantity next, but this time I wen with Humanism instead of Religious and OMG. Instafavourite for HRE - stacked boni mean practically no rebels ever, no Religious turmoil and 25% RU is very very tasty. My main issue was overestimating the power of Poland + Lithuania + Novgorodian Russia vs me, Austria and Mega France and slowing myself down by about 30 years. Ah well, was my first successful Ironman run anyway, will upload as soon as it's ready. Will know better for my inevitable Blobban Blobbich Blobbanov run as Muscovy.
Poland-Lithuania is the war that will make or break your campaign to Germany. I went super conservative with my MP, since my first 4 ideas were Influence, Administrative, Aristocratic and Diplomatic. 10% discount on all techs in the mid-game and 25% cheaper annexation compensated somewhat for my bad kings( my best was a 3/2/3, if I remember correctly). Still ended unbalanced on tech. It would be far worse if I got humanism or religious for the reformation, but I got humanism as the 7th idea group. Too little, too late, as I would not accept any new cultures, nor the rebellions mattered, as the biggest one was 3 stack of about 30k, and I had 300k soldiers at the time. If i got one or two more average kings, I bet I could've ended 32/32/32 and annexed Britain. Oh well.