Here's a sample of different hair groups used in Poser:

https://youtu.be/po5EF1PwtXs

It's "Poser Pro Sexy Manga Dancer Dynamic Hair Test" if Rosity nukes the link. There are three hair groups. Only one of them was run with collisions on. The other two were no collisions (which you can see when she turns her back - the hair in back goes through her shoulders).

(Though it's age-restricted, she's dressed, and the naughty bits remain covered.)

I like the idea of having separate upper and lower groups on the back of the head. Hair growing from the lower back of the skull isn't very important in most images (though you'd miss it if it weren't there!) I like the idea of being able to make that coarser, with fewer vertices, and save resources for more visible hair over it.