SWMM Treats Pump and Their Discharge Lines Differently Than the Implicit Engine. How Do I Handle the Differences, Especially If I Want to Use Both Engines?

SWMM can "model" a force main without accounting for the hydraulics of the force main from the pump. You simply specify the discharge node for the force main and the water arrives there. In the software, the hydraulics of the discharge conduit are explicitly considered.

If you want to get consistent results for a pump line in SWMM and the implicit engine, the force main should be represented as a "Virtual conduit" in the software.