I believe the point of the mod is to slow the growth of your settlements compared to vanilla in order to make your t1-t3 crap units somewhat relevant.

That said vampire counts don't care much about it because of the raise dead mechanic so you shouldn't be that bothered with growth in your settlements except with the income those high tier buildings give, which again you don't need that much since raiding/sacking can be very lucrative if you can reduce your upkeep by only using crapstacks zombies/skellies.

And about the tomb kings... Just take a necrotect when the game gives one to you freely in the first couple of turns, place him in your army, abandon khemri and use the incantation of ptra to reach tier 3 before turn 10, i can't think of anything else to make it faster in the early game.
Once you reach the point where you can recruit lords at level 30 though you can just break the game by recruiting tomb kings and taking "usirian the god of the underworld" then disbanding, rinse and repeat until you reach an absurd amount of growth per turn on every single province you own.
Of course you don't need to wait until level 30 but it allows you to avoid ruining your income with that pesky maintenance skill on your characters

Know what to nerf now :P.

i don't know if it's the mod slowing the growth as the changes to the growth requirements were made by CA. The thing is, it seems that the fast campaign submod doesn't help too much. Hard to tell as i don't know exactly by how much it affects growth.
You mentioned vampire counts but looking at the campaign i've played the slow growth hurts a little bit their army options, as from what i've seen you can't recruit blood dragon warriors (blood dragons on foot) and zombie dragons from the raise dead pool. By the time you have a tier 5 settlement you field so many armies that these new units added by SFO become useless as all the other ones can be recruited by raise dead at obscene discounts and these tier 4/5 units are REALY EXPENSIVE due to the increased recruitment cost from having multiple armies.