Questions about Joule Performance High End Gaming PC

I bought this PC and am very satisfied with its performance, quality and volume. How easy is it to expand this JP-PC with additional hard disc storage? Better M.2 or 2.5"? 3.5" is probably out of the question. I can't find any information on this, but I have seen in a YouTube video on a similar model that there are three 2.5" slots behind the right flap.

I am very satisfied with the stable, quiet and powerful system. At the time of my purchase, the price for assembling and testing the components was around CHF 600, which is more than okay.

I9 oke but wele generation 13 or 14?