Isn't this like "How to cope with Europe 101"? I mean, I don't think I have ever played a Europe game since I was a complete noob where this wasn't a massive part of my idea group selection process. Sure, sometimes I wouldn't actually take it, but I would know exactly what risk I was taking.
If you are playing in Europe and you aren't taking one off religious or humanist, you must have a plan to deal with the reformation. ....
That is exactly the same way I have been going. Game as a beginner in Germany. Reformation, auto-conversion, unrest, rebels, disaster => panic. What to do? Ah, take Humanist Ideas. Some decades later, after filling it out, problem solved. Lecture for next games: Take Humanist before the reformation. Plus it gives splendors already from the start of the Age. Works well.
In a fast expansion game it is difficult to complete an Admin group early. It is easier to pick #1 something like Diplo or Espi and #2 something military like Defensive/Offensive. Invest the Adm points in coring and going to Adm Tech 10. To open 3 slots for Idea groups and be eligible to form bigger nations like GB or Prussia.
Even more aggressive and probably more optimal in WC-theory is: Taking Admin Ideas as #1 or #2. Just filling out the first two ideas for -25% CCC. But then it is very difficult to have another Admin group early.
Having a plan to deal with the reformation: Yes, that is the point. Absolutely.
Flipping Reformed asap and quickly converting key provinces is what I am doing most of the time. The problem is here more the hit in the opinion of all Catholic nations, not the religious unrest.
For France I had another plan: Because Nat Idea #7 is +2 ToHer and +2 ToHea my intention was to stay Catholic and do it with the "Edict of Nantes" and temporarily accept the demands of Heretic rebels. As I got my achievements way before the reformation kicked in, I just think it is viable, but I don't know it for sure.