They will reflect the class ticketed. If you are in 1st Class then you will get 1st class SCs and miles; if in business then you will get business SCs and miles. There are a few routes where they do operate 3 classes domestically and there are some NA routes ( e.g. Caribbean ) where they sell J rather than F.

As far as SCs go, it does make little difference , since there are only a few routes which are 2701 miles or further ( such as BOS-SFO ) . For flights 2700 miles or less, the SCs are the the same whether in 1st or Business.

Dave