@Karen Moore good question, and yeah the burn from assuming matching is handled is a rite of passage with BLE modules — been there too.
The RF front-end on the MultiNav Pro+ does include the external amplifier and sensitivity optimization internally, so the matching to the 50-ohm port is handled on the module side. Your job on the PCB is keeping that 50-ohm environment clean all the way to the antenna — which with an inverted-F trace antenna is honestly where most of the range loss happens in practice, not at the module port itself. IFA tuning is finicky and very sensitive to ground plane geometry, so I'd strongly recommend budgeting a few 0402 pads in an L or pi configuration between the module output and your IFA feed point even if you end up leaving them unpopulated — gives you a tuning escape route after you measure.
For reference layout and RF port specifics, I'd ping RFOXiA directly through the Dev Hub or check the Resources section in Club — there's documentation and firmware examples there, and for hardware integration questions like this Moamen has been pretty responsive to direct questions. The 50-ohm assumption you're working from is correct as a starting point, just make sure your trace impedance is actually controlled (stackup matters a lot here, especially if you're on a thin 2-layer board).
And honestly for chasing the 50km number — that spec is drone-to-drone with clear LOS and no ground reflection, so if one end is handheld or near a surface you're going to see something closer to 5-15km regardless of how clean your matching is. Still worth doing it right though, every dB counts.
