DAS makes Genie Plus not necessary, but if you use both you will trivially get any park done. (Maybe not Magic Kingdom) We used DAS plus Genie Plus for my son with Autism and knocked out Hollywood studios in July with no problems. (All rides, and all shows)
One thing we realize about DAS in park is that like others have said its in use until you use it, but unlike Genie Plus you cant "miss" your window. (you can for the 2 pre book and Genie plus) Its used once you get to the ride then after the second scan you can use it again. Also when you DO use it, it seems to take the wait time of the ride you want, add that time to the current time and thats your return time. (give or take about 5 minutes) So it pays to pay attention to the wait time of your DAS selection if you want to optimize how you are handling the park and Genie Plus lane you have.
Very important is that the DAS holder MUST go on the ride for the group to board.
Finally and most importantly. It works for Individual
Lightning Lane rides at no cost. So you can use it to guarantee Rise of Resistance, Seven Dwarves Mine Train, Flight of Passage, Frozen. Im not sure how it works with Guardians sense thats virtual queue. I believe you still have to get a virtual queue slot before you can get that one. (I might be wrong about that)