It's hard to say.
Sidelining the VP in favor of someone else would be a very unusual thing to do, especially since the Democrats have made such a big deal lately of putting black women in every possible position. Having made such a big thing about black women it would make sidelining the black woman VP even more of an unusual thing to do, especially if they replace her with a white man. The inevitable accusations of tokenism would be all but impossible to counter.
Aside from that Gretchen Whitmer has the advantage of being female even if she is a white woman. Gavin Newsom is widely commented as being very telegenic and apparently the liberal cities in California love him. Whether he'd bring out the Democrat voters who might stay home rather than vote Biden is hard to say, but it's hard to see him having any appeal to moderate Republicans and given the news reports from California I wonder if he'd have much appeal among independents. But then he isn't the orange man, so we'd potentially end up with another election where each candidate's primary attraction is that they aren't the other candidate.
