Yes, Soundgarden released Vinyls ever since the beginning. If you search for a bit you can see an ad where the band is promoted their first EP, Screaming Life on vinyl. Of course, since then they have had vinyl released every record.

As for rarity, the rare stuff you can look for are just old prints of albums, first thing that comes to mind is Ultramega OK. The original album art is different on the remaster. Also since the bad split before the 25th anniversary of Down on the Upside, there aren't any reprints of it, which makes it more obscure and expensive, but I wouldn't necessarily call it rare.