[Alneyan]

Having Dominion level 10 or Dominion level 5 does not really affect that, however: your core provinces will reach maximum Dominion (equal to your base Dominion + temples) without any problem, and once it is done, they will no longer be targets for Dominion spread, at least until you get 5 more temples... but getting +1 will be easy enough when left unopposed.

Dominion spread on a spiritual border will result in heavy "fight", with nobody likely to have a maxed Dominion for long here.