One question: for partner bookings (specifically BA), it seems that the reservation picks up OW status based on the FF number and then allows things like seat selection. If mrs. brp is Sapphire (LT Plat), will it still allow both of us to pick seats right at booking by noting that one of the people on the itinerary is Emerald, even if the FFN of the other person is Sapphire? Or will I have to call to have this recognized? Never faced this situation before

I've been able to assign seats on the website for companions without any status on same reservation. Regardless, it seems that OWS get advance seat assignments on BA anyways.
https://www.britishairways.com/conte...ving-your-seat