"Now, something like a VacuFlush comes in 24V. Do folks pull 3x8=24V from the bank to power 24V users?"
No. Or… I should say, they shouldn't. The vacuflush is, admittedly one of the limitations if you are installing new heads since they don't make a 32V. Raritan does and the Atlantes or whatever the current model is, is a popular choice if replacing the Oem GMs. Of course, some folks use a separate 12V bank for a 12V inverter/thruster or whatever and, in that case, a 12V VF can work from that bank.
I have installed two (additional to OEM) converters to power some added 12V electronics but have never needed more than a 10A model. It is more effective/efficient to use several smaller converters as opposed to one large one, simply because you can place the new converter close to the equipment, powering the converter with the 32v system which will already be fairly close to the new components, thus avoiding the addition of many feet of much heavier gauge wire that the 12V item will require.
Obviously, if you want to power a high-wattage 12V device, you may need a larger converter but again, you want it as close to the component it is powering as is practical. IOW, placing a single large 12V converter in an engine room and then running 12v wiring from there all over the place is not as efficient…and a lot more work/expense.
