In Cali we pull our fastpasses in the park. Now they have maxpass we can pull them from our device but we still dont do it in advance. I guess my question is do you have to schedule your passes 30 days in advance? or can you just kind of go with the flow, play it by ear and pull them the day you are in the park?
Fast pass booking opens at 60 days if you're onsite, 30 days offsite. Yes you can get them day of, but the availability won't be the same. That said, you'll likely be able to get most things, but you possibly won't get the best times.
If I was going on a WDW vacation, I would never wait until day-of. I would book them as early as possible - especially for the headliners (i.e. the Pandora rides, 7DMT, FEA, etc).