You can't go wrong with tri tip and there's no need to spend extra $$$ on Prime or waste time sous vide-ing. Garlic salt and pepper are all you need to season. You can also try making slits and placing garlic cloves in there.
As far as prepared rubs, I've used John Henry's and Pappy's
https://www.pappysfinefoods.com/ but I prefer just the garlic salt and pepper.