Trading off to pull more amps is not really feasible. Power is the work done, the product of voltage and current. This is what (watt) is being delivered to the water, ultimately. You can achieve this, in a very basic sense by either increasing the voltage or the current. However, a quirk of material interaction with electricity is that it is the current draw and the resistance that have a heating effect, I²R. However this is in every conductor, including the ones you have packed in behind your walls. This also means that if you deliver too little voltage to a product designed to pull a certain load (a given amount of power) it will make that power up instead by drawing more current, and hopefully only destroying the product, which I hope is cheaper than your home.

Additionally, your point about doubling the voltage is correct. If you took a live feed from breakers off both sides of your “split phase” distribution panel, that would actually mean you were delivering 240VAC @60Hz to an appliance, at the loss of your neutral line (frequency interactions are another consideration to an item) but many ships around the world work happily without a neutral line.

This is all very basic a way of looking at it. My apologies, I’m tired and not a teacher.