Previously the VIP tour allowed you front of the line access to any attraction with a FP-. I wonder if this is still true with FP+.
If so then the value of a VIP tour just went way up since there are more attractions with FP+ than FP-.
It is. Every FP+ attraction (with the exception of just a few character M&Gs), plus one without FP+ (TriceraTop Spin at DAK).
I would decide what you really wanted to do, but not plan everything exactly. Remember that is the tour guide's job. A really popular version is the "highlight" tour -- if you're ready to push it, it's possible to do the headliners of each of the four parks in the six hour minimum.
If you want a more relaxing pace, and don't care about sticking to the minimum time, you can get almost everything done in all of the parks in one day. Not just headliners.
It's still suggested to start early. While the advice to wait until later in the day so you can do more things yourself while its less crowded is sound, remember that you're still going to be walking through the crowds later in the day, and tour guides still have to wait in the FP+ queues, which can get a bit backed up during peak times. Also, if you stick with just MK, its pretty easy to start at nine and have everything with a line done by three (the six-hour mark). You can save things like the Peoplemover, Monsters Inc, the Carousel, Tiki Room, etc, for later. OR you can still set up FP+ for the afternoon after the guide leaves. But if you wait to do the guide a little later, when it's busier, it will take them more time to get through things.
Of course, it all really depends on what you're looking to accomplish with the tour -- the guide is there to help you do almost anything you want to do!