We actually tested this in Florida this past April. Outside temps were low 90s with 80%+ RH. With the Chill Cube in Dry Mode, the highest we saw inside was high 70s and 55ish% RH.
So it didn’t quite get below 50% humidity, but it made a huge difference. At 77°F/55% RH it was comfortable enough to hang out in. In those conditions I’d say 55-60% RH is probably the realistic best-case without adding a separate dehumidifier. Bear in mind our Brinkley 5th wheel is not as “efficient” as an Oliver.
We love the Chill Cube, the variable speed compressor is very efficient, we have seen similar numbers than @jd1923