Hey Heliox

Welcome to the forum

I’m not very experienced in building a cnc router and currently under the design stage an when I’m done will put it up to be judged lol from what I’ve ne reading an researching, I think your budget might need to stretch abit more if your looking to do aluminium aswell, there’s plenty of people who can refer you to contacts to get parts cheaper an deals, also don’t order your electronics until your design in in place as things will change and you don’t want to be stuck with parts you’ve brought that aren’t no good,

The design your looking at if you go onto the guys channel he has got a build log to give you a better understanding of his design, and I believe them Nema motors your looking at are too small nM wise, I think they would suit a 3D printer more, the standard seems to be 3nM or more from what I’ve read.

With regards to the spindle water cooled is the best option, for the amount of noise a air cooled produces and at low speeds might not cool the spindle efficient enough, again people can give you contacts to sort that for you with a vfd to go with it, best thing is start with your design and there’s plenty of sticky threads to help with your design an then go from there.

Again I’m not a expert but there are a lot on here so just thought I’d give you a few things from what I’ve been looking at and reading, looking forward to seeing what you design

All the best