Do they? I remember seeing this in the past but can’t find the information anymore. Now they only say “all major search providers” and that was part of the criticism in this “reveal”. That they have become more opaque rather than being transparent about it.

This is all the official info I could find. Please share if anyone can find anything more. https://help.kagi.com/kagi/search-details/search-sources.html

Not that I know of. I don’t know much about the service to be honest but I use it when I feel like doing some exploring and then I just use the website and browse for things that looks interesting.

Maybe not exacly what you’re looking for but www.chosic.com has a bunch of tools for recommending similar artists and songs.