Power supplies in this application are basically voltage regulators, the battery itself is the amperage regulator. The power supply does no amperage regulation other than not being able to provide more than its rating, it regulates the voltage and the battery takes what it takes to climb to and match the power supplies regulated maximum voltage.
All charge controllers are basically just voltage regulators whether it be an alternator, a converter, a smart charger or a power supply.
I assume two power supplies can be run in parallel without confusing each other.
I do not think you need 2 MW's with the powermax 75 amper, just disconnect the powermax and switch to the MW once the PM drops to the premature and oh too slow 13.6v. At that point, at that state of charge, the MW should be able to hold 14.8v with no issues and rise to 15.5x no issues either if so desired.
