We just got back a week ago, and I don't think the overplanning hurt our trip at all. Really, I think the key is to categorize it into research and actual scheduling. Finding out what is there and what you want to go to before you do helps a ton, especially getting everyone's input. I made ADR's just in case we happened to be somewhere (but only 3) since we were not using the
DDP, there was only 2 of us and we did mostly counter service or ate at the resort.
What we actually went with was a schedule of what park I thought we'd go to each day for the first 5 days or so of a 9 day trip. I followed the UG crowd level and stayed away from EMH parks. We basically followed the touring plans for the things we wanted to see but would do repeats etc of rides if we wanted. I don't think the touring plans are really necessary if you hit rope drop and do the big rides first unless it's really crowded. Neither of us are into parades and just took photos of DNiece 11 with any characters that happened across our way.
Planning and reading this helped a ton though to know what we would want to see and what would be oh if we have time type of things. Also, DIS helped me pick the resort which we loved and made me pay attention to that discount postcard I got in the mail. It also helped to say ok, this is vacation and I talked with my niece about everyone else trying their best to have the most fun they can and that can make people seem rude but really they're just trying to do what we are.
Also, I did use gardengrocer and having water bottles and breakfast foods in the room was essential. We also did the cheap glow bracelets and handed out our extras at the P&PP which made some other people's night magical as well. Also, I ordered a thumper/bambi best friends basket from the disney florist and had it delivered at the end of our first full day from "our pals at disney".

That remains the most magical moment of the trip for my niece, that this mysterious gift just showed up for us, even beat out getting the dream fast passes at AK for her.
So thanks DISers for all the help planning and believe me, I don't think any of that was time wasted, I wouldn't have known about any of those things. Once you're prepared and know what you're doing, it's easy to just let the scheduling flow.