Sounds good. If you’ve got someone to help you setup the welder for welding batteries, I would ask them.
The welder looks simple enough and applicable. Though I dont have direct experience with that model.
I run a 10s4p as a cruiser as well as a last mile board
His welding service? it is dirt cheap for the effort
bro as someone who built an esk8 before for school. You want a small board and what you’re building is gonna be cumbersome to hold. build something the size of the boosted mini. try hub to reduce weight. 5ah -10ah is plenty. i recommend trying to modify your board so that it will able to be charged with USB-C PD. SO you don’t have to bring an extra charger. depends on your weight, i think 29 - 35 inch is perfect for a commuter board. good luck