Not so much #1. It's true that YC companies get attention on HN, but they have to struggle for it like anyone else (not counting the Launch HN posts - see below). We help them sometimes, but we help non-YC startups too, and the question is always what the community will find interesting. YC startups probably have an edge on HN, but if so, it's for more subtle reasons (e.g. the fact that YC alumni have always been a core part of the community).
Definitely #2. The job ads that appear on the front page are only for YC startups, and that's one of three formal ways that HN gives back to YC in exchange for funding it. The other two are that YC startups get to do Launch HNs, which get placed on the front page (see https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...), and YC alumni usernames are displayed in orange to other YC alumni. For some reason I always forget to mention these things when writing on the above topic, I guess because I don't think they add up to the biggest thing, even though they're significant. In my mind the big thing is the connection to startups forming and applying to YC. However, no one has ever tried to measure these things, and I'd feel a bit queasy about doing so. It would feel like stepping out of the magic circle in a fairy tale. One should not step out of the magic circle.