If you ever talk about tech in a backpacking forum, it seems inevitable that you need to be prepared for at least some minimal interference pattern from folks that might like the HYOY mantra in theory, but just can't resist ...

In terms of apps, when you get around to hiking the AT the suite of apps you'll want will be somewhat different than the ones that you list now. I suggest that if you have a smartphone that includes a GPS chipset, for the AT (and for very few other trails ...), having maps on the phone is sufficient --- it's what I did last year and would go that route again.

A voice recorder app is sometimes handy. Book reading software for times like, for example, you're in a laundromat waiting for your clothes to wash and dry. Internet capability (definitely to include wi-fi in towns) is handy for a variety of reasons, not least of which is to get an occasional weather report (I like the ones via postholer.com mobile version, which is also a great journal site for a mobile device). It's also important for me to be able to upload my cached daily journal entries when the stars align to make that reasonable. FWIW, I like to carry a folding bluetooth keyboard to make it easy to type up a journal entry each night on the trail at the end of the day, but perhaps the on-screen keyboard software will be sufficient for you (I do suggest practicing all of this stuff on one or more decent length shakedown hike(s) to work through inevitable issues beforehand).

You might also consider using your phone as your only camera, though practice with this ahead of time to ensure you're happy with it. I was; the AT isn't that scenic, and a phone camera (especially these days) is plenty for still scenery shots and pictures of people, which is most of what I take on the trail. I was able to get pictures of moose and other slow moving animals, and overall that was fine, plus the photos were then already on my internet capable device for direct uploading when I got to town (time plus power plus good connection ...).

It can be helpful to put a variety of documents on the phone; for example, I have a couple of first aid "books" on my phone to augment a terse, small-print one-sheet set of first aid info that I carry. The pdf for the manual for my watch is on there. And one of the AT guidebooks (the AT Companion) is, or at least was available in pdf format. I carried that on my phone, and AWOL's AT Guide in hard copy, and that seemed like a good approach.

Best of luck in your prep!