My understanding is that the tribe voting power is only reduced for votes that match the corresponding tribe tags/metadata. So you would spend 2% Hive VP for each 100% vote on Hive, but only reduce the tribe VP if the post matches the tribe settings.
You can find the tribe params here:

You can see that there are per-tribe values for voting power reductions (*100, so 200 == 2%) regeneration (in seconds), cashout window, curation, etc... https://scot-api.hive-engine.com/config?token=BBHO