I don't see much of a reason to doubt Tristan's alignment claim, especially since Johnny apparently corroborated it. I suppose they could both be scum, but it'd be a really questionable play for them, to say the least. As for Tristan, I'm not convinced he isn't a killing role, and he obviously wouldn't tell us if he was. I think there's likely to be a vig (or some town-aligned killing role, at least), but it's not necessarily a certainty. Whether we kill Tristan or try to find scum today depends largely on 1. our estimation of which roles there are and who they'll target and 2. how confident we are in our ability to get scum today.
If I'm understanding Legacy's post correctly, there's no real chance of us losing today if we lynch Tristan. There is a chance of us losing, however, if we leave Tristan alive, although it would require mislynching and the vig failing to hit scum, too. So it seems like the safer choice is simply to lynch Tristan today: not only would it remove the uncertainty of his role, but it would give us more time to potentially find scum the following day, with the vig possibly hitting one in the night as well.
I'd rather not place a vote now because we still have time, and I want to think through this and avoid pushing a wagon beforehand. But it seems to me like our best option is simply killing Tristan now, especially with the absence of strong scum reads from most people, including me.