This video explains how to do it for a orange pi (he uses a different OPi board but the process is the same).
Option 1: USB charger -> usb cable [solder and insulation tape] jumper wire with dupont female at other end -> male pin header on board (makes the connection removable)
Option 2: USB charger -> usb cable [solder and insulation tape] jumper wire [solder] pin header [solder] board (not removable) like this and this
you'll need to make sure the jumper cable can carry the required amps and exposed areas are insulated.
I have no recommendations on the second part of your question though.
