Raising voltage will make your stock alternator capable of more current, but how much, if any, will depend on the rotor & stator design. When you raise output voltage on the alternator, you are also raising the voltage across the rotor coil, making it a stronger coil, which in turn makes the rotor/stator combo a higher amperage
A given stator wind needs "X" amount of magnetism from the rotor to reach its maximum capability. If you have a weak rotor coil that doesn't pull much current, you’ll gain output by raising voltage. If you have a strong rotor and a relatively low amperage stator you might not gain anything because you are at full saturation to begin with
After years of designing rotor/stator combos for different amperages and seen as little as 5 amps and as much as 60 amps worth of gain when raising voltage. A properly designed alternator will gain very little when raising voltage
Maybe the confusion comes in when people try and compare something like a 110v air compressor and a 220v air compressor of the same horsepower. Everyone knows the 220v compressor will pull less current but that's for the same amount of work being done
If you happened to run 150 volts to your "110v" compressor, then it will pull more current and effectively become a higher horsepower compressor setup. Some people take comparison of that and try to apply it to car audio amplifiers and get confused
One might think running higher voltage to your amplifier will make it pull less current which it might, for the same amount of work, "wattage" being produced, but odds are you are going higher on the volume, so really you are making your amp pull more current
Then you can get into regulated and non-regulated amplifiers which make it even more confusing to most people without an electronics background