Does the battery ever get full while running that load, even during the day? Float is for after the batt gets full, so it ought to depend how full it gets and how early before dark.
The solar would have to be supplying all the load's amps to allow the LFP to also get some amps so it can get to full. You then have a time it stays at 14.6 or whatever--is that too long before dark so you need to drop to float before the voltage drops anyway in the dark?
Brain not working--but if the batt is full and the solar is doing it all, is the loaded voltage 14.6 or is it lower from the load? Is the loaded voltage already low enough to count as low enough for no harm done? As said brain not working--probably stupid thought :)
I see the PWM vs MPPT in the OP is not about that as such, but is about what settings the controller has, whatever type it is.