I will only add that such an enclosure needs sound dampening if you want to be around it without earplugs while it’s running. The best material I’ve found for sound dampening is Rockwool Comfortboard80 - 1-1/2" compressed fiber-batts that are stiff enough to screw/washer onto a frame.
In fact I made an entire enclosure for my SPROXXL out Comfortboard80 for a short-term stay in a basement sitting. Afterwards I felt my main CNC cabinet, while over-built, did not provide nearly as good noise suppression. So I took out the nearly useless acoustic foam panels I had mounted inside it to replace with Comfortboard80 which helped immensely.
Also I would suggest that you build your enclosure with plenty of space above the CNC for dust collection hose movement & head clearance when placing/removing materials.