This is probably OBE, but buy the untrimmed. I've grilled/roasted/smoked enough tri tips to reach into four figures. Grilled two just two nights ago. Still eating on one of them.
Costco is selling either Choice or Prime grade. I buy whatever's on sale. The two I grilled the other night were Select grade ($2.98/lb), and were still beautifully marbled and tender after 25 minutes direct heat to a rare/medium rare finish and a 30 minute rest.
I usually trim about 6 to 12 ounces of fat off each tri tip, leaving about 1/4". I don't bother removing the silver skin.
I've made them all the ways you've mentioned from grilling to smoked to 190F IT. The grilled to rare/medium rare and the 190F IT are my two favorites. Direct heat on the grill is my go to, about 12-13 minutes a side.
Get 'em, enjoy 'em, and share the taste.
Cut across the grain, which can be tricky with a tri tip. It can have three grain directions.