I have been using Gaia GPS on my iPhone this year and I am really happy with it. I tried it a couple times last year and wasn't that impressed but a recent update made it much better. I even took to leaving my Etrex Vista at home because everywhere I went I found Gaia could get a lock.
If you shut cellular data off or just go into airplane mode it saves a lot on battery juice in the mountains.
Be sure to download an area you are going to before you get there if you think that area has questionable data connectivity.
So my phone is my maps, GPS, camera, video camera, communications home (with InReach) and ballistics computer all in one package.
As far as charging I did try to use a solar panel for a bit, but sunny days in the fall in North Idaho are not real common so I have switched over entirely to using a battery pack.
The Mophie Juice pack powerstation pro is only 6000mah, which was pretty good when I got it a couple years ago, but there is a better one for less money now that has double the charge for the same weight. I forget the name of it but it was mentioned on another thread concerning batteries.