Are you full hook-up or do you go off grid a lot? If the former, you just need a simple converter that can do 13.6ish volts and enough amps for your 12v systems, usually a 55 amper will do.
If the latter, then the size and type of converter needed depends on your battery bank size in AH, your generator size to be able to run the amps size of the converter, and how long you run the generator.
Also might matter what voltage charging specs your battery type has, whether the converter can do those voltages. An adjustable voltage converter is best for that consideration.
