I've been trying to research this topic lately. I'm torn between having a 20k mAh battery and two 10k mAh batteries. My plan is to have my phone on all day minus sleeping, in order to use OnX or GoHunt app. And will probably only be using inreach mini to send checking messages in the morning and evenings. I will also carry a backup rechargeable headlamp, which I hopefully will not need to use or if I do hopefully will not need to recharge.
As of now it is unclear if I will have a base camp or not and whether or not that will be near the truck or not. If we can come back to the truck every night the will likely not get a solar panel and will probably go with the 20kmAH battery. But I do like the idea of having a 10k charging with the solar panel at camp while I am hunting carrying a fully charged bank.
As far as solar panels, outdoor gear lab has some good product reviews and the big blue 3, although it could be heavy depending on your weight needs, seems to be a good option. What I am mainly looking for on a panel is one that has good charge interruption recovery, meaning if a cloud or clouds pass over for a while, when the sun comes back out the panel will go back to putting out full power. Some panels from what I have read, will stop providing good output when cloudy and when the sun comes out don't start putting out full charge unless you unplug and re-plug your device back in, meaning you have to babysit it, which is not practical and not worth taking if that's the case.
My other question on solar panels right now is, can I get away with a small solar panel such as a 5 watt or 10 watt for charging a 10k mAh battery pack or should I go with the bigger heavier 20-28 watt range panel?
Back to the battery banks, I would look for one and have been looking for one that has QC technology for sure on the output, meaning your devices will charge faster, but also on the input. They do sell some that have the PD input, you have to buy a separate 30-60w wall charger, but can charge a 20K mAh battery bank in 3 hours. I think the QC on the output is probably more important though.