Lil' Marco isn't going to be picked. The Biden campaign would immediately go on air with all the Rubio quotes from 2016 how he described Trump as a fraud and conman who should sell fake watches on Fifth Avenue.
Rubio would be the best possible pick for Trump. It would mean Trump is reaching out to Haley Voters(those who were actually Republicans) and reaching out to neocons in general rather than going all in on Paleocons .
Vance would be a terrible pick as that means Trump is gone full on in pandering to paleocons and the tucker types.
I think Burgum would be the best and safest pick. He's inoffensive and comes off as a calm force, what could reassure some conservative swing voters. Rubio on the other hand just seems like a lightweight and the brand of neoconservatism is toxic as hell.