Tip: DO register your rewards account stake key as one of the owners (I did it for my pool), so with two real people, you have three owners. In that way the rewards do count towards determining if pledge is met. So once rewards are accumulating, an owner can decide to withdraw some funds from his/her payment address without violating minimum pledge and without asking the SPO to transfer some of the rewards. Notice though it doesn’t matter for the pledge counted in the rewards formula, there only the amount registered in the pool registration certificate matters; any pledge above the minimum just counts as normal stake (I think…).
Rewards account balance only counts to live stake if the delegation certificate is registered on the blockchain (during pool registration or just as regular delegation certificate registration).
If you redelegate an owner address to another pool, the certificate of this delegation replaces the one from the pool registration (this is the same as changing delegation with a ‘regular wallet’). The ADA from this owner doesn’t contribute to pledge and stake anymore. Also, the rewards from the new pool will be received on the stake address of this owner (instead of on a pool rewards account).