you definitely should give WHFRPG a shot as a GM (id recommend 2e over 3e). thatd make that world make more sense because it was literally made for it.
as for the setting by itself, that can probably be as simple as using any other setting tbh. theres a warhammer wiki and a book available on amazon
This game got me into the lore as well. I found a pretty basic encylopedia that seemed like a decent overview. https://www.amazon.com/gp/product/1560251719/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
Otherwise, I would look into the army books for any faction you're interested in. I found the Vampire Counts especially interesting since it had a whole section on the Von Cartsteins. At least the edition I got