Coupled inductor vs an actual transformer?
You don't have to use coupled inductors in a SEPIC configuration.  The main advantage is that you can get by with lower inductance windings.  If the two inductors are closely coupled, the ripple current is divided between them and the required inductance is halved.  So if you want to replace a coupled inductor which has two 3.3 uH windings, you would need two individual inductors of 6.6 uH each at the same current rating.