Is the Innokin Jem suitable for sub-ohm direct-to-lung vaping?

No, the Innokin Jem is not designed for sub-ohm aka direct-to-lung vaping. It supports coils of either 1.6 Ohm (included with the kit) or 2.0 Ohm which are available separately. You can order spare coils for the Innokin Jem here.