Which lands should be grouped together on each day?
It really depends on your goals and options.
If we are staying at the resort, then we will want to take advantage of early morning entry. If not, then we usually go the park that does not have early morning entry.
In general, we don’t focus on specific lands. For example, we might go to one park, do as much as we want/can, then go to the other park the next day and do as much as we can. Focusing on the rides that are most desirable, taking advantage of the MaxPass/Fast Pass system.
I use subsequent days to fill-in. Go on rides that you want to revisit and/or ones you missed the first time around.
5 days is plenty of days. You should be able to go on every ride in the park and see every show.
We’ll be offsite this visit so only one early entry.
My plan is Mon: DL
Thur: DL (early entry)
Fri: DL leaving around 8 to head to airport.
I wanted to keep each day in adjacent lands so as to not walk all over the park. We did that our first day last trip and our feet never recovered
I would do FL on your early entry day. To minimize tired feet we often use the train, monorail, Main Street vehicles, and trolley whenever possible to get around the parks.
I always like to have 1 DL start on the West side (either in Critter Country or New Orleans) and spend that morning focusing on the West side. If Fantasmic! is running this will be a good night to see it either by working in a dining package option (all on the West side) or pulling a FP first thing (by the dock of the Mark Twain which is straight on from the Frontierland entrance- to the left if facing it).
Then my 2nd DL start is always in FL getting as much done up until ToonTown opening (which is 1 hr after reg park open, 2 hrs after early entry if there was early entry that day). Doing this on your early entry/Magic morning day will make it so that you can prob do almost all of FL before ToonTown opens. That leaves your afternoon open to do some shows/entertainment like Storytelling at the Royal Theater and Mickey and the Magical Map, two very well done shows. I do also love being in Tomorrowland at night so I like to plan for nights in Tomorrowland on this day. If this day is a weekend (or you’re going during peak Spring break or after Memorial Day), then watching fireworks from the hub/Main St is a great way to end it.
Then with a 3rd start in DL I would start at Tomorrowland, hit a few of the rides & then return to Main Street and ride a vehicle, ride the train in the full Grand Circle Tour loop, visit the firehouse, opera house with the Disneyland Gallery & if you like history (or need a nap) visit Lincoln, enjoy the characters/live entertainment throughout the afternoon in Main Street & FP the rest of the rides in Tomorrowland. This day is a great day to pick up missed atractions in any other lands or repeat favorites.
For DCA… you could split it up as Hollywoodland/Grizzly Peak one day and Pixar Pier/Paradise Garden Park the next day with Carsland both days, once in the daytime, once a nighttime because it is so beautiful. Be sure to plan for seeing the neons turn on at sunset. If WOC is showing do this one night. If PTN is showing do this the other, plan for Carsland at night for whichever one works best around the showtimes.
And I definitely agree with the advice from @carthy15 to use the train, monorail to save your feet! Hope you’re planning goes well & please ask any other questions you have!