I’d suggest spending a little extra and going for a bigger motor. It doesn’t cost much extra and you’ll get better performance. I wouldn’t recommend the 3D printed motor mount. Others have tried and they’ve failed on them only after a short amount of use.
For vesc configuration it’s super easy. There’s a step by step playlist on YouTube that you can watch which makes it very clear. Don’t be daunted by the setup and configuration process, the complexity isn’t far off from being plug and play
As far as the battery goes if you want to do it yourself you’ll need a spot welder. Otherwise @barajabali should be able to help with a prebuilt battery.