I would avoid a Flipsy ESC, they can be sketchy. I would recommend Maker X.
I had a similar first build to what you’re proposing, check out my thread. I’ve gotten up to 46 KM per hour on this deck and I don’t see myself pushing to go faster.
For the enclosure, you should find plenty of people on Facebook marketplace offering 3D printing services. You can hunt down some 3D print files from https://www.thingiverse.com/ too