Thanks for all the insight here. With the new tighter Avios availability across non BA partners, we are struggling with finding inventory in a unified ticket flying BA metal on an AA ticket. We are trying to go SFO-LHR and then continuing to ARN. I am seeing availability on BA metal available to book SFO to LHR via AA (my preference since it requires far fewer miles and I have more of them) but onward to ARN I can only book using BA Avios. Does this mean that I will need to retrieve my bag, clear customs, recheck in LHR, etc... seems like a massive headache. I could purchase a unified ticket from SFO through to ARN using Avios but it would almost double the required miles (and I have far fewer Avios).

About how long do you think I would need if I were to keep the split tickets (there are two layover choices, one is just shy of two hours which seems tight, the other is almost five hours which sounds miserable)

Any guidance would be greatly appreciated on best practices or ideas.