As soon as you decide what parks what days, make your reservations. Especially for HS as that seems to book faster. You can always change them.
The positive of no FP means do what you want. See a ride you want to ride, get in line & ride it. If you are there early for RD then try for a headliner or 2 before the lines get long & then check on them thru out the day. I think the lines keep moving pretty decent since they aren't being interrupted to let FP riders in (unless they have a breakdown or something). Don't be scared of the lines that look long. Remember they have parties spaced apart so of course it will stretch out further. I have found usually I am riding the ride sooner than anticipated (not by tons but 5 or 10 minutes). It was a little odd at first, but I have gotten used to it & enjoy my park days more. I don't feel like I am always looking at a clock or worrying about being somewhere at a certain time. If I want to stay longer & watch animals in AK, I can.
You do have to stop to eat or snack so that was weird for me too. Usually I would snack along the way to another area or ride, but now I have to stop & sit down to eat so that also changes how you traverse around the park as well too. And when I say "sit down" sometimes it's just grabbing a spot on a rock or bench or something along the way that you're spaced away from people so you can remove your mask. It's actually been sort of fun to find new little spots to eat or snack and enjoy the park I normally have blown by before without a thought.