Help with first build. Power and button input

[groovytoney]

Hello guys. Long time lurker here. Attempting my first gameboy build. Im using a Pi 4 though and a 6 button PCB but only using 4 buttons...considering using the other two as shoulder buttons. My question is how do i connect the pcb to the Pi4 though? Can i wire the buttons directly to the GPIO abnd map them that way? Im trying to avoid buying a teensy or using an AIO pcb. Will the buttons, volume wheel, and other stuff wire directly to GPIO or wuill i have to get another PCB anyway? Could i just u a blank breakout board for it? And i also bought a PS Vita joystick...is it possible to control this via GPIO and have it function correctly also?

Also., as far as the power issues....Im using a 3.7v 10000 mAh battery. I know i will need a step up converter but the powerboost 1000c seems inadequate. I may have found one on amazon that outputs up to 24v/6a. I figured the 3a suggestion for the Pi 4 wouldnt be enough but it powers the Pi 4 and screen fine so far with no lightning bolt icon. MY question is how to wire the battey to enable the boost converter and also allow it to charge correctly and if possible, charge while playing also. So would it go charging board --> boost converter --> battery --> Pi power input or what? If that makes sense. Apologies folks im pretty new to this scene. Any input would be appreciated.