to answer that question;
low profile box section rims arent the most rigid of rims, they deflect easier than say a rigida dpx or any other high profile rim,
but by using a high spoke count you can create a strong and comfy wheel, a high profile rim on the other hand holds its shape much better and therefor can be used with lesser spokes.using a dpx rim will there for also give a much harser ride then a low box section rim.
also; with a lower spoke count you in general need to increase the spoke tension but as someone else said before; those old aloy rims, if the really are from the sevnties, will be soft as butter meaning that the rim wont stay straight between the spoke's;hard to explain but imagine the rim would zig/zag left to right from spoke hole to spoke hole
mavic low profile rims are only sold with spoke count 28 or higher so reflex or open pro 28 holes or more, when mavic offer a wheel set set with a low profile rim, mavic classic the had a spoke count of 32 holes
campagnolo neutron out of the top of my head have spokes, i think lowest spoke count on a boxection rim i have ever seen was 24 holes on a front wheel in a fir wheel set, and that was missery !!
on the otherhand, have you ever seen a wheelset, whichever brand with a high rim and a high spoke count ? plenty of examples of low spoke count/high rims wheels around...
hope that helps you a bit (-: