This is an isolation transformer so yes you can omit the galvanic isolator. Yes you can set the output to be either 120 or 230 volts regardless of which input voltage you connect to.
You will still need to put input circuit protection on board the boat before the transformer and it will need to be 32 amps when you are connected to 120 volts and 16 amps when you are connected to 230 volts.
The main difference between the MultiPlus and the Quattro is that the Quattro has two AC inputs, one for generator and one for shore, and automatically selects the active input, so no manual transfer switch needed.