There is no express lane for American at US CBP preclearance they have to line up along with all aliens. Since most people in line are American or Canadian it should move relatively fast.

You need to be Skyteam elite plus (KL equivalent) to get DL Sky Priority privileges.

There is no DL Skyclub for US bound passengers, only KL Crown Room for Intl passengers.

DL YYZ DTW are all on CRJ single cabin regional jets. Larger carryons which is OK for the larger jets will need to be gate checked.