If I have 3 days, my basic plan is this, I am not sure how much OBB interferes with this plan:
1) One day at DL, limit yourself to 1 half the park (everything except FantasyLand, ToonTown, and TomorrowLand). Once you get all you want to do at that half of the park, you can do repeats or try and start hitting some of the FL or TL rides, or park hop if you wish.
2) One day at DL, do the rest of the DL park, and do repeats as you wish.
3) One day at DCA. Do what you wish, and park hop if you wish.
If you go to WDW and are used to the rides there:
Out of the rides that exist in WDW, you should definitely do the following:
Space Mountain, Pirates, Thunder Mountain, Haunted Mansion (since configured in holiday mode).
Note that Runaway Railway, the queue is much improved and fun to go through. The actual ride though is mostly the same.
You can probably skip (near identical experience, or not as good): Peter Pan, Small World, Under the Sea (DCA), Soarin (DCA), Philharmagic (DCA). Small World does have the "hidden" Disney characters during the ride, but it's not that much of a reason to go on it, unless you really enjoy the ride.
Maybe skip: Winnie the Pooh. Rise of Resistance, Millenium Falcon.