Any reason to prefer this over https://nyaa.si/view/1752934 and its parts updates? A compilation of webnovels would work, but anything official is already included in that other one.

Depends. If you want these novels (like altina, black summoner, re zero etc) using this one much easier but if you download another light novel than use officially translated light novels or search on nyaa. In the end this one not cover all novels. Btw; Re Zero volume 26 is webnovel but you can find light novel version on nyaa.

Depends, i am not sure if Gamba replaces "cleaned" books with "clean" books, even if they are the same version. I rather have clean book for archiving than cleaned books, as in, removed any pages from sites that ripped it and injected pages. Like if they would only add a line on the credit page with their site or what ever, but no they completely adjust the structure...