What kind of balance is necessary for Democratic tickets?

[Mister Mets]

In discussions about potential Democratic tickets, there is usually a lot of focus on the balance.

Barack Obama and Hillary Clinton both had white men as running mates, and shortlist contenders. Obama also considered Tim Kaine and Evan Bayh, while Hillary's second choice was Tom Vilsack.

One podcast I follow speculated that at this point Democratic tickets will have racial and gender balance, and we did end up with a white man selecting a woman of color. One of the Veepstakes finalists was Susan Rice, who did not have conventional qualifications (she never ran a campaign or headed a federal department) which shows how important it was for Biden to avoid an all-white ticket.

There is an argument that Biden boxed himself in by promising to select a female running mate, before the Black Lives Matters protests subsequently made a racially diverse ticket necessary. If the protests had occurred earlier, maybe he wouldn't make the promise and would have been in a position to consider African-American men (Cory Booker, Cedric Richmond.) It could also be argued that after a female candidate won the popular vote, Biden needed a female running mate, but that this dynamic isn't the case for future tickets.

What type of diversity are Democrats going to select for future tickets? Will it be important not to have two white people or two men? Alternatively, will it be important to include a white person and a man? How might things change in the next presidential cycles? How do religion and sexuality play into this? Would this dynamic be shaped by milestones? For example, if a woman is elected as President, does it make it more acceptable for Democrats to nominate two men?

[Non Swing Voter]

Kind of feels like Democrats have this tendency lately to want an older and younger candidate.  They'd probably do MUCH better with two young candidates.  Of course, by "young" I mean like 50, which in politics is young.