First subdomain. I think HA is completely right that proxy with a subpath is basically an anti-pattern that just makes things worse for you and is always a bad idea (with very few exceptions).
It’s only an “anti pattern” because app developers are, on the whole, lazy bastards that start out hard coding stuff and then get discouraged at the amount of work needed to fix things after the fact.
I should know: I am one of these people.
It’s crap, it’s best to roll with the punches and use a sub domain.
That’s energy, not power. If that’s the energy consumption per hour, then that’s 120W, which is high but not outrageous with a full size computer with 6 disks.