Flying AA LHR-MIA on 23/7/22 so now departing T3 rather than T5 but staying at Sofitel T5 on 22/7/22.

I wondered whether we would be able to use fast track security at T5 (BA silver/flying business class AA) and then connect airside via the bus or do we have to use the free connect train landside and use T3 security which looks busier than T5. If the latter is fast track easy to locate as I've seen recent pics with long queues and no separation until nearer the security entrance (been a long time since we've flown from T3 I can't recall the layout).

We should have our boarding cards and dealt with luggage on 22/7.

I'm wondering whether we would be better off changing to the later BA flight from T5 (we had originally booked the early BA flight but that was cancelled and we were auto rebooked onto AA57) but not sure that it would be allowed given that I accepted the change to AA.