I was able to customize my Magic Band and select FP+ times (which are now listed under my reservations, along with hotel and ADR's). Staying at Yacht Club beginning August 17. (Actually, will be at AoA starting August 14, but they don't seem to be eligible.) When I logged into MDE, there was a pop-up screen that told me to customize my bands and select FP+ times. It wasn't something that I had to go search out.
However, I didn't get an email, so I could actually be a tester, or it could be a glitch. I was given a phone number to the My Magic+ IT people, who confirmed that there is a test in August, and the system is live for the testers. Emails for August testing are still being sent out sporadically. They wouldn't/couldn't tell me the hotels or dates, just that they thought it was through August 25th or 27th. (She was pretty unsure.)
I'm not a fan of FP+, but I decided to try it out, gambling that we will still be able to access regular FP as in the last round of testing. (Also, our YC stay is only 4 of 11 park days, so I'm not locked in for the whole time.) One frustrating thing, though, is that I have two old tickets that I plan to upgrade to an AP once I'm there. Since I only have two days worth of tickets linked to my reservation, though, I can only reserve FP+ for two days.
For those who are wondering, I was able to book 3 FP+ at a time, one park per day. There were no limits to headliners -- got Soarin', Test Track, and Mission Space at EP and Toy Story, ToT, and RnR at HS. It gave me options A-D for return times, and then I could try and change the times later if I wanted to.