My take on boob armor:

Historically, the most common form of defense a woman has is called a "man."

If you have "serious" lady-warriors in your fiction, you're either appeasing male feminist nerds, or you're trying to titillate weeb nerds. Design the armor to your audience.

If you have lady-warriors because you want male feminists to soyface at your media and Buy Next Product, then for sure, don't have boob armor. If you're trying to sell waifu pillows to permavirgins, then your boob armor needs to be no smaller than DD. It's that simple.

This has nothing to do with "realism." "Realism" is you either have lady "warriors" because your overwhelming tech superiority has made war safe (i.e. US Army), or you keep the women out of harm's way while the men do the fighting.

Just get the out of here with this "realism" crap. If your lady warriors aren't getting the absolute piss beaten out of them by male opponents, realism was never your concern. They're slower, weaker, less durable, and more easily shellshocked than men.

Just admit to yourself *why* you have female warriors, and that will determine how your armor should work. I'm totally fine with making women have the same armor as men. Admit it's to appease feminist nerds, same reason we have women in the US infantry.

People are gonna cite historical exceptions that prove the rule. These are nearly always either women who didn't actually fight (Joan of Arc) or women who were part of a last-ditch effort to repel the onslaught of an unstoppable enemy (Red Army in WW2).