What's a normal range for unison and generic "two-part mixed" choir?

Title. I'm assuming I should follow the advice I heard about writing for a congregation and keep it between C4 and C5 in treble clef wherever possible.

I've also got the impression that in a two-part mixed choir, the male voices sing part 1, rather than part 2 (obviously both in an appropriate octave). Is that correct, or is it more flexible? Alternatively, is it something the director decides instead of the composer?