https://recipes.anovaculinary.com/recipe/sous-vide-barbecue-beef-tri-tip would be a decent guide to what you’re tryin’ to do.
Skip the BBQ sauce in the bag. If that’s what you are after, you can do that in a crock pot for $30. Even Kenji Lopez-Alt wrote an article or four on why boiling meat in a bag filled with sauce/marinade/oil via SV yields sub-par results.
What I did and still do with an unknown cut is look at kenji etc. Pick the doneness temp and do it in a Ziploc so easy to check.
So the tri tip was awesome!!!
Tender through and through. Couldn’t ask for a better outcome.
Next up, pork roast.