From the help reference:
wrapwords (ww)
Similar to, but different from, vi's auto-wrap mode (i.e.
"wrapmargin"). While inserting, words are moved to the next line
if the current line gets too long. Wrapping is only attempted when
a space is typed. The target maximum width of lines is changed
with the "fillcol" setting. (B)
Would is be possible to add new-line to the set of characters that cause
wrapping to occur? I find the last line of a paragraph frequency violates the
fillcol value when I insert a new-line instead of a space or when I go back
and correct text that runs past the fillcol value. This does not happen when
I use the wrapmargin setting. When using wrapmargin it seems that wrapping is
implemented as characters are typed rather than waiting for a space character?