Yup. When I was first learning electrical stuff, comparing it to plumbing was exactly what I did. The alternator is your water pump. The resistance is the diameter of your pipes (low resistance is big pipes). The amount of water flowing through the system is current. The system pressure is voltage. Your battery is the water tower that the pump feeds. Your pump is only good for so much water output and this can be used as pressure, flow, or a certain related combination. If the pipes are too big (resistance is low and too much wattage draw on the system), then your pressure and your flow will be augmented by the water tower until it runs dry, then you're on whatever the pump can supply directly. But on the other hand, if your pump is too powerful for the system you might break some pipes or even your water tower.
For your testing, I would skip the VAC side of things. AC checks are only useful to see if your alternator is functioning and, on their own, they are not useful for determining alternator output. The reason for this is because the internal resistance of your multimeter is very high and you probably don't know the exact value. You might be able to use another multimeter to figure it out, but then we start getting into Inception-like scenarios. Measuring current directly from your alternator may cook it, so I don't recommend that choice either. And, ultimately, it's the DC side of the equation that's running the bike and charging the battery, so we should be measuring DC.
For the battery, overcharging was not the same consideration in the 70s as it is now. The battery was actually specifically chosen because of the beneficial effect it has on helping to regulate power within the overall system. You may notice that some of the early twins and singles don't even use a voltage regulator and that's because of how the battery acts. A battery with an overly large capacity is more resistant to overcharging than one with a small capacity and so you'll often see batteries with a 12Ah capacity put on relatively small motorcycles, even those without electric starters. With a flooded cell lead acid battery, there will reach a point when the battery is fully charged and the voltage differential between your circuit and the battery exceeds about 1.5V. For instance, lets say your system voltage is around 15V and your battery is floating a full charge at 13.5V. When the voltage differential between the plates in your battery exceeds that threshold, the additional power your system is generating goes into electrolysis. You start splitting the water molecules in your electrolyte into Hydrogen and Oxygen atoms and additional power also gets lost as heat. You had to periodically top them up with water. So the batteries were specifically chosen to compliment the charging system so that they could help ease the burden on the voltage regulators, which still had a ways to go before they could handle the task on their own. A modern voltage regulator will almost always permit the use of a smaller battery on an older bike because the battery is no longer serving in the capacity of an auxiliary voltage regulator. The inverse is also true: Modern batteries don't play nicely with older voltage regulators.
For Zeke, I would pick whatever interests him the most. I work for the College of Engineering at Oregon State and both are growing programs with good placement after graduation. It's purely anecdotal, but it seems the EECS (Electronic Engineering and Computer Science) students seem to do better in our neck of the woods because of the presence of Intel and Microsoft. I'm not sure there's a"bad" engineering choice at the moment. Our economy seems to be in a transition away from manufacturing, but we still do a heck of a lot of design. All the stuff you see manufactured overseas is still being designed and engineered over here.