thats hard :/
vampire mods can be seperated in different categories: those that just change vampire powers, attributes and abilities - those that add quests and clans, and those that change the core scripts to modify sun damage and blood vials aswell as the vampirelvling...
my old mod
jaysus vampire mod for example adds hoods against sundamage and drinkable blood vials... thus changing the core scripts and being incompatible with other vampire mods... if youre good at loooong texts and scripts you can try to combine the advantages of different mods that do such things...
therefore open the scripts of each mod (namely vampiresomin scripts) and merge em somehow... but this can be quite difficult....
a rally good vampire mod is still missing however, one that adds clans, quests, places and uses all the nice gadgets like blood vials and sun protecting clothes... there are clan mods but none is really the top notch mod... most are ok tho
best is to try em all out and see which aspect you like and then start working your way through the mods... youll have to learn scripting and questing for sure, models and so on are easy in comparision.
good luck