Wife-H means wife of head; 1930 enumerators seem to have used this form; I have found it in several states. I don't think that you actually do have any Wife-N entries — I think the apparent Ns are merely blurred entries.
In one 1930 census I examined recently someone was listed as wife of grandson (or something like that) but the relationship was spelled out in full.
Wife-H does not mean wife of head. It means homemaker or housekeeper. In most cases the wife of the head will be this person, but in some cases you will see it on a daughter or daughter-in-law or other family member, particularly if the wife of the head has an occupation listed. It was an attempt by the census to determine who was actually doing the housekeeping tasks in the home when women were beginning to move into the out-of-home workforce.
I found it on ancestry.com. You don't need to have a membership to read about the different censuses, just to look at the actual census data. On the home page, just under the search box, is an area labeled "Browse our Collections." Click on the year of the census in which you are interested. You will get a page with a search box for that census, and underneath the search box is all the defining info on the census.