Higher voltage as in you mean charge faster or higher capacity? Higher capacity and "thin and light" are *usually* two opposing concepts. That said, higher capacity isn't always better. As I've mentioned before, when I travel, I usually have two ~10k mah power banks rather than one 20k. The reason being, the 20k can take an incredible amount of time to charge (this may have changed in the last few years, but these are the banks I'm currently using). It's easier to have one bank charging and one in use as the charging one has more time to top up. If I were to use a 20k, it would never be full (assuming I drained it enough) for most of the day.

I do have a 20k which I keep at home, mainly for extended power failures and to power "other" devices.

At home, I leave my phone on wifi while I sleep as some of my apps back themselves up and it lessens the data usage. But when I wake up, I usually go onto LTE to cut power usage. I've heard 5G consumes more power (heard, haven't read studies on this topic yet)... but if 5G is just as hungry as wifi, then I'll likely stay on wifi when at home.

In general, it depends on what you are using your VPN for. It doesn't hurt (although the power hit might not be worth it), but realistically it is just a shift of who knows what about you (and if the VPN really doesn't log your information). Whether it is the VPN or your cell phone provider, someone knows at least something about you. I don't do anything really important on my phone to have it engaged (no banking apps or any sensitive information on my phone in general). About the only reason I would have it on (day to day) would be to prevent IP based tracking apps (as compared to "location-based tracking") from knowing where I am.

Keep in mind, in general, you're also taking a performance hit when on VPN...