Being an earl (or a viscount) in the Tudor period didn't go along with any particular administrative duties, which is likely why you're having trouble finding resources on the topic. I have a previous answer that discusses this:

At heart, the origins of most titles relate to the rank/scale of the land that a given nobleman had administrative duties over. "Marquis/marquess", a title from the Continent, at one point referred specifically to noblemen who controlled land on the marches (borders); the title of "earl" in England comes from the early medieval ealdormen who were in charge of entire shires; "viscount" was likewise originally a continental title, and it once went to men appointed to assist counts with their administrative duties; "baron" has a complicated history in England, where it was imported by the Normans to refer to all noblemen who were (for want of a less loaded term) direct vassals of the king. By the High Middle Ages, though, English titles were becoming detached from these definitions of duties and simply related to a system of rank that gave each a specific position in relation to the others: dukedoms were invented to give to male relatives of the king a status, while baronetcies were invented for the other end of the system, and everything in between lost its administrative function. With the addition of more and more titles to honor men who'd done services for the crown or who'd paid for them through the late Middle Ages and the Early Modern period, even the association with related lands was often lost. (This did not happen to the same degree on the Continent - dukes ruled duchies, counts ruled counties, etc.)

It's hard to put into words what these titles were beyond "just things people refer to them as", because that's basically what they were by the point you're asking about - centuries later, Lord Melbourne would explain to the young Queen Victoria that one made a man a marquess if he merited high reward but shouldn't be made a duke for some reason. Titles often went along with incomes from rents from certain estates or with high positions in government, but all that they were intrinsically was a statement of social status relative to other titles or people with no titles at all. Henry VIII made Charles Brandon the Duke of Suffolk to raise him above the other noblemen at court, and to make it clear that they were very close.

I'm not sure what there would be to read, because nobody really explains it: it's just something you're supposed to understand from context. I think The English Nobility in the Late Middle Ages by Chris Given-Wilson might be helpful for unraveling this in more detail, though.