I have a flight from the USA to Prague. First leg to LHR is on American and the second leg LHR to PRG is on BA. I have a seat assignment on American but BA doesn't assign seats in advance for ordinary folk (unless they pay). According to the BA website, you can check in online 24 hrs in advance (or less) and get a seat assignment at that time.

So, if I do OLCI on the AA website using my AA confirmation code once I am at the 24 hr threshold, will this also check me in to BA and get me a BA assignment? Or do I have to find out the BA confirmation code and check in separately on the BA website? Or do I have to wait to I get to the airport and get an assignment and a BP from AA in the US, or from BA once I get to LHR?

Also, the BA website says that the checked bag allowance LHR to Europe is one bag. AA allows two free checked bags. Will BA try to hit me up for a bag fee once I get to LHR, or will they just accept the two bags since it was an AA codeshare?

thanks for any tips