Worst:
I mean the biggest thing is probably the one related to the topic. J-women will always put up a play fight when you try to seduce them which can be incredibly jarring at first. First time I heard "Stop! I don't want it!" I was taken aback and pulled away. But then she looked at me like I was an idiot for stopping. It comes in varying levels but you pretty much have to expect it and be super tuned in to the non-verbal communication.
In the relationships I've had I had asked the girls if they could stop doing the resistance thing, and they complied, but in both cases told me that not doing it made them feel uncomfortable. One girl's perspective was that she felt like a slut if she didn't protest a little bit. The other girl said it turned her on and it wouldn't be exciting if she didn't try to push back a bit. I cannot wrap my head around it but even in serious relationships it is probably something you will have to deal with.
Best:
While things can be confusing when making a move as described above, the opposite is the case beforehand. Girls will never ever come up to your apartment if they're not 100% down with it. You can say "Hey wanna come check out my place and have a drink? I have a cat and he's fluffy" or whatever and she will absolutely not go if she's not ready for you to make a move on her.
In the West, I've found that girls don't have this filter and will go with you to your home just for the hell of it. Then when you make a move you can get the "whoa what are you doing!" which will never happen in Japan.
The plot of the JAV video above was completely sealed the moment she sat on his couch and agreed to have a drink.
Puss:
As for puss, J-girls have pretty much all had the same pussy size and shape. Idk whether you'd call it innie or outie but probably innie. In my whole life I've only ever been with one girl who'd I consider to have a definite "outie" where the labia sticks out more than, say, a quarter inch. It's weird because in porn you see a lot of girls with huge labia flopping around but in real life there's not ever much hanging out.