If you make 2.1 you could add some info on the port forwarding because there are massive differences on it between providers. Like PIA gives you a single random port that changes each time you reconnect, while AirVPN gives you 5 static ports you can configure yourself.
AirVPN lets you open 5 ports and allow p2p. Works with their app and openvpn/wireguard. I've been paying for it couple years now and I'm pretty happy with it
What should I use if I just want dumb file storage that is accesible from any device (linux/windows/android) remotely? I'm already self hosting a media server if that matters
Could it be because the phone spends less time in the charging state?