Power Bank questions

"Power banks" can cover a fairly large swath of products. With that said, current battery tech is fairly optimized at this point. All things equal, the size of the battery will directly correlate to the amount of energy it holds. The first decision you need to make is how many times you want to be able to recharge your phone and cross that with how portable you want the battery to be. If you're good with something that just lives at the house, you can now get into some pretty beefy batteries that can keep devices juiced for days at a time. If you want something that can fit in your pocket, you're looking at one, maybe two charges max. Just depends on what you're looking for.

You just missed the Prime day sale, which included many Anker products. They run sales for father's day, etc. too. They are a little pricey, but I've still got power banks from them that work just fine from 2014. One of my biggest can recharge an iPhone 5x before needing to be recharged, and it's one of the oldest, and I think I paid $45 for it back in the day.

I wouldn't worry about overheating, just don't do dumb stuff like put a black power bank in the sun while charging, don't use it underneath a pillow or blankets, etd.

Another thing that is super cheap, and proves very useful during disasters is a power inverter for your car. $17, and you can charge phones, laptops, etc.