From our experience (we're hard core refreshers, and were just there in June/July)
1. We all have Android phones
2. We use our own data, the WiFi is a bit spotty simply because so much demand is placed on it.
3. For us, we always book our first 3 FP+ for as soon as we arrive. We're not rope drop people (we think FP+ and refresh make rope drop totally unnecessary), so if we have a morning planned, we'll show up at 9:45am or so. Therefore, we'll schedule our first 3 FP+ for 9-10am, 10-11am, 11am-noon. When we arrive at 9:45am, we're already at the back end of FP+ #1 window. We go right to that. By time we get off, it's already time for #2. We go right to it. While in line for #2, I'll jump on
MDE and move #3 up to 10:30am. So as soon as we get off #2 it should be time for #3. When I'm in line for #3, I jump on MDE and go for #4. Rinse and repeat. If we have an afternoon planned, we'll do the same thing, just starting later in the day. Honestly, we found this summer trip a bit harder than trips past for refreshing, but still had plenty of success. Understand however that our definition of "success" means getting a FP+ for 5-10 minutes from "now" so that we can literally just hop from ride to ride...unless we're planning lunch, dinner, a show, etc...so we set high standards. Even with that, we still had plenty of success. In a 6 hour park visit, including time to stop and eat, we probably average 6-8 FP+. We also do some attractions w/out FP+ simply because they aren't needed, such as Philharmagic, CoP, etc...
4. You'll have much better chances to add/modify the day of your FP+ plan, instead of trying 24-48 hours in advance. Not saying you can't have success one day out, but day of is much easier.