It seems OP that most of your post you seem to focus on questions related to Hagrid's rather than whether you should have a plan as a whole for the trip.
That being said, if your focus is on Hagrid's all I can think of is just keep an eye on the Universal app for the wait times, as well as keep checking the thread, specifically a week, or so prior to you arriving for your vacation to get a more accurate representation of what is more currently going on with the ride at the time.
I say this, because if people have been checking the thread, it seems that Hagrid had a good streak and then things have drastically changed within the last week. That being said, we can see how quickly things can change and how process can go forward, then backward, and repeat. Since I do not know when you plan on going that's all I can think of doing is checking the app, as well as keep an eye on the thread a week, or so, prior to your trip to see where Hagrid is at the time.
As for planning, no, I do not feel you need it. The minimum I would do is research the rides, find out what you want, and go for it.