We are long time WDW vets, who have fallen in love with DLR as well. DLR is so much easier and more flexible.
Universal Orlando is easy- especially if you get the express pass. On a whim this past October on a Monday we cancelled our WDW dining reservations for the next day, bought a 2 park universal ticket and express pass, and spent the next day at Universal. No planning necessary. We grabbed an uber from our WDW resort- got there at opening and left at closing. The one thing about Universal Orlando to know is that if you want to ride the Hogwarts Express (which I highly recommend) you have to have the 2 park pass because it goes from park to park. If you only have a 1 park ticket- no Hogwarts express. There are some things you can plan in advance like certain dining reservations if you want them.
As far as WDW--- Disboards- especially the Theme Parks and Strategies, Resort, and Restaurant forums are your friend. I would suggest looking at the different crowd calendars there are around the internet to try to plan your park days. We don't do rest days--DD made it clear at age 2 that wasn't an option and nothing had changed on our last trip when she was 12. We usually do 2 or 3 days MK, 2 days EPCOT, 1 DHS and 1 AK. Don't know what Star Wars Land might do to that plan.
If possible, you want to book your resort (assuming you are staying on property) more than 180 days ahead of time. Dining reservations (ADRs) can be made 180 days in advance and if you are staying on property then you can book dining for the entire length of your trip (up to 10 days from arrival day- if you are staying longer than 10 days you can't book that far out). Allears has all the restaurants, menus and prices listed so you can see what appeals to you. Some restaurants do book up at that 180 day mark so it is best to book that day. I get up at the crack of dawn and book everything. I would say book something-- and then later you can change things around or cancel meals you decide not to do. I don't think Counter Service food at WDW is even close to as good as at DLR in most places- so I would go nuts. If you don't have a resort reservation yet, you can book one day at a time starting that 180th day from arrival-- but remember you are competing with people who have booked their whole trip's dining reservations already.
There are benefits to staying on property. Booking the ADRs for the whole trip is one, but the main benefit is being able to book your FPs at 60 days instead of 30 days. That can make a big difference on the most popular rides. WDW is not as flexible as DLR because it is not as easy to get same day FPs. With everyone booking 3 for the day in advance, it really limits availability. It is so much easier at DLR where you have to wait to enter a park and then book 1 at a time. As far as staying on property, unlike at DLR where all three on property resorts are really expensive--- WDW has 3 levels of resorts- deluxe, moderate, and value. You can stay at a lower price point and still get the on property benefits. Lower priced resorts are not the ones that are closest to the parks-- you aren't walking to a park or taking the monorail or boat to a park from a value resort (although there is getting ready to be a sky gondola from of the value resorts to DHs and EPCOT). Value resort rooms - at least the standard ones- are typically smaller than the rooms at other resorts.
A real issue with FP+ is the tiers in some of the parks. Because there are not as many attractions- outside of Magic Kingdom- the other 3 parts have tiers and for your 3 advance FPs-- you can only get 1 of the Tier one rides. For example- at EPCOT Frozen, Soarin, and Test Track are all tiered so you can only get 1 of those as your 3 when you advance book. Also, until you use 3 in that park- you can't get another tier 1 in that park. (Now- if you were to only book 2 in advance- and then use those and hop to another tiered park you could get a tier one in the 2nd park even though you have not used all 3 in the first park---- but I don't want to get to technical and completely overwhelm you in this first post!)
If you love character meet and greets, Kenny the Pirate is a great resource and well worth the price of the subscription.
So--- the first thing to do is pick a resort--- hopefully before the 180 day mark. Then, you want to figure out what parks you want to go to which days-- crowd calendars will help. Also, know that EMH parks are typically the most crowded parks that day. If we are going to do extra hours-- we typically will do those and then hop to a different park-- we aren't super early morning people, so we usually will hop and do evening extra hours here and there and ignore the morning hours. Once you have figured out which day for which park- then you need to figure out the dining that appeals to you and book ADRs- preferably at 180 days from your arrival day. Then, assuming you are staying on property-- you want to nose around the Disboards, figure out the most popular rides for FP, and decide what you want to FP so that you can do that right at 60 days. Again-- book something right when you first can and then you can play around with it later if you want to tweak or change plans.