Over volting can be fun as Kirstin says, tbh parts for hub bike sare generally cheap so not a great deal if a controller blows or a hubs fails.
I have only ever run my hubs at max controller current to see how fast I could go, think the most i saw watts wise was a tad over 850w with my q128c.
I usually run my hubs at 13 or 20% of controller current for my needs and that is also for towing, I often don't feel the need for more power unless i come across very hillyterrain or a one off steep climb. My current g370 is paired with a 22a controller so in pas1 I only see 125/130w or 2.86a in pas 2 I see 195/200w or 4.4a.