If you favorite an album in Tidal, it is added to your library in Roon, and the primary artist is also added. Vice versa, if you add a Tidal album to the Roon library, it becomes favorited in Tidal. This is how the interaction between Roon and streaming services works
Roon works essentially on albums. If you favorite a single track in Tidal, the track will be added to the Roon library as one track from an album. I.e., the album will also be added to the library, and it will appear in the album view, though there will be only one track in it, plus a button to add the rest. The album’s primary artist is added to the library whenever the album is added, hence in this case as well.
So, I guess that if you favorite a playlist on Tidal / add the playlist to the library, this might pull in the tracks and with them their artists. But I’m not completely sure about that part.
I don’t think there is a way in general to prevent artists being added together with their albums from streaming. A big part of Roon’s ethos is that the source of music (local, streaming) should not matter and it’s all presented together as equals.
I don’t think you are missing something. ARC is focused on mobile playback and is a version 1.0 (that has quite a few open problems so far that need fixing). It’s quite natural that proper Roon at home has many more features at this point.
Searching for artists in you library vis “Search” can be slow and painful so I add 1 x Album of a given artist to my library if its an Artists that is currently not represented in my library. My Tidal favourites are actually quite few.
That now means my Artists view now contains that name so I can now use the much quicker Filter Funnel to get to an artist with a few letters typed rather than waiting of Roon searching my my Library and Tidal (and Qobuz) , now you can get to the Discography in a few key strokes
A second shortcut is to keep a collection of your “Top xx” Artists in a Tag and name it 01 - Artists so its always the first tag shown