>>5789358Not a woman but I'm into dudes. The basic appeal is just to make the guys cute/hot. The sake way that regular anime style might emphasize ways that women are cute/hot (making the smaller/curvier, big expressive eyes, slim parts, bouncy tits, etc) bishounen and BL art styles emphasize shit that makes guys cute/hot (expressive eyes, hair, a defined face, muscles or soft parts, etc).
If you want to know what makes guys hot then just search up the gay or m/m tag on gelbooru or wherever else and take note of the most common features, or look up the highest grossing bishounen and learn from there.
An emotional detail that you probably won't catch though is that the audience for this shit likes guts that they think can love them. Sweet guys are especially hot but any guy that you can imagine having a soft spot for you and only for you is the ideal.
