Some people say it automatically sets your best outside defender on their best scorer, others say it is whoever you set at PG. I think I have only played outside box and one one or two times (quite awhile ago), but I personally think it is more reliable and you'd be better off by just setting up M2M for defense and place your best defender at the spot where their threat is.
Murray/Harris/MPJ/Grant/Jokic - 2020 NBA Champs