Don't see what PWM vs MPPT has to do with it. The battery doesn't care--solar is solar. Voltage goes down every night, which sort of counts as floating for any type of battery, depending on the scenario.
The concern over float voltage with LFPs seems to be more with converters left on for long periods. With solar, float voltage settings should also depend on the scenario? Is this just for when camping or for when the RV is sitting at home for long periods?
If the latter, the usual story is run the LFP down to 50% SOC and disconnect. Get your 12v from the converter.
While camping off grid on solar I guess it depends on how many days/weeks in a row and whether you get to full charge or not and even when during the day that is. It still gets dark at night though.