A full Avios redemption does not earn Tier Points. If it was a part pay arrangement, so a commercial ticket where you used Avios to reduce the cost, that would earn full Tier Points according to the fare bucket.

To change the frequent flyer number, well it's not that easy, but one route is to use the Royal Air Maroc site to remove your BAEC number and then add the RJ number in BA's Manage My Booking. If you have not made the booking, then you best buy the ticket on behalf of yourself. So don't buy it under the default name, buy it as if you were buying it for a friend with the exact same name, address and date of birth as you. If you have a reservation with RJ on it, with seat reservations, your only option is to swap to BA after you have a boarding pass, otherwise you may lose the seat selection. That means dealing with it at check-in, or calling up, and can be an uncertain process.

If you are going to do any RJ flying you may want to consider them as a permanent home, but usually running two lower level cards in the same alliance is more trouble than it is worth.