For me the query "!guix nginx" returns the following sites:
- https://guix.gnu.org/manual/en/html_node/Web-Services.html
- https://packages.guix.gnu.org/packages/nginx/
- https://guix.gnu.org/manual/en/html_node/Certificate-Service...
- https://guix.gnu.org/cookbook/en/html_node/Setting-up-NGINX-...
And some results from the GNU Guix mailing list. !guix searches with a custom lens[0] that I added for Guix specific documentation and resources like the mailing list archives, and the IRC log archives.
I can combine this bang with the quick summary feature (accessed either by adding !q to the search as well, writing a query that ends in a ?, or pressing the q button after loading the results), which is essentially the same as the info boxes that Google will add sometimes, except it only shows up on Kagi if you specifically request for it.
I have also mapped versioned documentation for some things to the latest documentation using url redirects[1]. I have also manually hidden or raised lots of sites that I don't care about or care a lot about. This manual curation makes it so your search results get better over time, without having something like Google try to deeply understand who you are and what you want to try to figure out what search results are best for you.
Kagi specific features have been very integrated into my workflow personally. I definitely find the subscription worth it.
[0] https://kagi.com/lenses/l7mPOuJp7zljHquBjsekFn6dM9Thw1A8
[1] https://help.kagi.com/kagi/features/redirects.html