How are mixed choirs organised?

[Lisztener87]

If you are writing for a medium/ large mixed SATB choir (80 singers approx), are the Sopranos and Altos female and the Ten. and Basses male as a convention?

How common is it to have Men and Women both take S, A, T and B registers and how is this reconciled given women can't sing as low as men and men as high as women?

There are multiple ways of organising the voices for either male or female singers but if someone could talk about some common conventions or any other recommened set-ups I'd appreciate it.

Thanks.