Unless at least one of Murray or White has made a quantum leap from 3, they'll probably mostly split the PG minutes, with White probably generally closing.
The reason they'd bring White off the bench in that scenario, is the fact that he'd obviously have a more featured role with the bench, where his superior play making is more needed.
But if White is ready for a Siakam like breakout, then what? They're not good enough to play politics, so it's either start him at SG, sub at the under 6 in the 1st and 3rd, then alternate him and Murray ala Aldridge and Gasol (this likely requires running a 9 man rotation) . . . or trade DeRozan.