Whilst I am not 100% sure, I thought that only two bags are allowed for free with sapphire status on a choice ticket, and am not sure AA will honour the previous 3 bag allowance if on separate tickets. You can certainly check luggage through from BOS-SMF, but worst case scenario would be having to pay $25 for the one extra between LAX\SMF. Not that it should make any difference, but I also think that those flights are operated by compass airlines.