Thank you for posting your request on History Hub!
I regards to your search for a list of enumerators assigned to specific regions, I might suggest reaching out to the Census Bureau, to ascertain whether or not they retained records of enumerators and the areas to which they were assigned. They might also be able to provide more information on whether or not enumerators were allowed to report on their own households.
There is an extensive history website available for the Census Bureau here:
And, here, a link to their pages on the site which give more information on how enumerators were instructed for each census year.
A list of regional offices for the Census Bureau can be found here.
You may be able to contact a regional office to ascertain what historical records about the enumerators were retained for the area in which your great grandfather worked.
I hope this is helpful in your research!
Very helpful - thank you!