Oh, and just noted here - if you want to form the HRE faster - convert to another religion (non-gamey would be just converting to Reformed or Protestant (I suggest protestant, the production efficiency REALLY helps when you form HRE) when either come up), then enforce religious unity. Each conversion gives you 10 imperial authority, so converting the whole HRE will pretty much let you form the HRE pretty quickly if you had good DR with the minors & have a few vassalized (since vassals are very easy to convert).
You can also just enforce religious unity on electors (that'll only garuantee your spot as the Emperor, better just enforce it on everyone and do it last on major powers, so they have no chance to get elected, altho it's really unneeded if you know what you're doing, very easy to make electors vote for you), so if no other major HRE powers are protestant/reformed - you'll get all the votes (electors don't vote for nations of other religions AKA heretics/heathens).