Chit Chat would be by far the most popular, it's the general discussion forum.
Layout? Well..not for the Forum home page (
http://www.nzboards.com/forums), but you can collapse the categories to hide forums...
Thread-wise, if you click the Thread Tools link at the top of the first post in a thread, you can change from linear mode to Threaded mode...that changes the Thread layout.
You can sort forum display listings by date or by reply count or other options, these are at the very bottom of each forum.
Regarding custom avatars, that is a
Supporting Member priviledge.
For information on what each standard Rank can do,
click here and for the benefits of Paid Membership,
click here 