p171 - unit confers Scout to DT if they are deployed inside it; any Transport with Scout may have a unit w/o the rule embarked.

For the question of which units can be selected, doesn't seem to be anything that I can find that contradicts the literal description of any unit in the army, except under Allies it specifies that only BB can benefit from the warlord trait - so my interpretation would be you could not choose a non-BB unit. So choosing DE or Harlies - ok, but SM - no. But that may be open to others' interpretation of what it means for a unit to benefit from the WL trait.