This is tough to answer because the every day is different and the in-park variables are always changing. Here is what I can tell you from my recent trip:
1) We made an ADR everyday of our vacation, but by the end of my eight day trip, I wished I had made less ADRs.
2) You don't need Genie+ every day of your vacation unless this is your once in a lifetime trip and you will never come back. I purchased Genie+ for one MK day and one HS day. I do not see any value in Genie+ for AK or Epcot.
3) In addition my Genie+ purchases I bought 1 ILL attraction (fancy ride) two different days (once at HS, once at AK). It had no issues enjoying everything I wanted to see at AK without Genie+, as I was able to purchase FoP. There is no need for Genie+ at Epcot.
4a) I tried both Genie+ strategies. For my MK day, I entered the park with Early Hours, knocked out three attractions, had Genie+ and my first LL selected for the 9 o'clock hour. Once the park opened, I ate breakfast and then hit my Genie+ ride and just began selecting my next ride and going there immediately. I had a great day.
4b) For my HS day, I bought Genie+ and ILL for Rise of the Resistance. I booked my first LL for MMRR at 11:30, then went back to sleep. I woke up after the park opened, got ready and ate at the resort. At 10, I was waiting for the bus while I selected my next LL for another afternoon time. I just checked back every two hours and booked the next thing. Both of these methods worked for what I wished to accomplish.
5) There is a point in the day when Genie+ attraction availability just dries up and disappears. You want to be sure that you feel like you got your money's worth out of the system before that. Disney says that the average guest is getting 3 attractions out of Genie+; I got many more than that. I would feel like only 3 attractions is not worth $15.
6) The most difficult part of the whole damn system, is trying to coordinate LL reservations around ADRs. It takes more focus than I would like (on a vacation) to remember when my ADRs are coming up and figure out my travel times on the fly, while refreshing the app to grab LL reservations. It is not easy to do. ADR's at hotels or another park will really call into question the value of purchasing Genie+ due to travel time.
7) I have heard reports of many people having to make a decision between losing value on their $15 Genie+ purchase or being charged the $10 no-show fee for missing an ADR. Guest Relations 'should' be able to help you with these overbooking issues, but it is not guaranteed.
The whole thing will be on you, the user, to manage while you are in the park. It is not a difficult system to figure out, but the whole Genie experience definitely complicates your day as well as adds a lot more stress than previous systems. You don't have any way to practice before hand other than watching and refreshing the tip board prior to your vacation, but I didn't find that it was that helpful.
On the other hand, I think you will be fine navigating the system once you start using it. You will hit some of the bumps that I mentioned above. Reconsider a few ADRs on days that you want to really use Genie+. Ultimately, don't let it stress you out. Enjoy your vacation!