The motor definitely dangles low. Makes for a bit of a low break-over angle. But with respect to things that have all-tires off the ground like jumps, or general comfort street riding - no issues. Can go up and down curbs just fine. I just can't take it over say..... One of those bumps for car parking, or a log in the middle of the trail.
With my current config, I'll top out around 32-33mph on flat. That's with knobby tires and a relatively upright riding position. With my older (smooth) tires, I'd get 34-35mph. That's with the fenders, rack on it, backpack, street clothes. I'm sure I could get closer to 40 if I was riding tucked in and didn't have the other stuff on. But that's not really my use case - I wanted something comfortable I can commute on as well as have some fun.
It's funny that y'all mentioned the cs-rk3. That's the exact hub I'm running, coupled with an 11-50t wide range. Have a gear for every occasion!
No complaints so far with the UPP battery itself, though the included charger should be thrown in the trash. Long story short, there's a diode isolation setup on the charge port (which is good) that is bypassed when the battery is switched on. The charger's output voltage seems to be designed around plugging the battery in with the unit switched off. It outputs 59.5v - which would charge beyond 4.20v per cell. Lifespan wise, the battery seems to be holding up decent. Last time I checked capacity on charge, it was 11.8ish aH out of a rated 13. It's 8 months old. Take that number with a grain of salt though - the last couple amp hours are going to be really depending on how I discharge it / voltage sag when the motor cuts off. I really need a few more months to plot degradation over time. I know you can get actual battery testers. I just don't have one.
Range wise - honestly that's really difficult to say. It's extremely dependent on how it's ridden and how much I pedal. Really just need to familiarize yourself with your own riding style and just do math from there. I hate to give a nothing-answer, but that's about the most accurate I can give. OEMs generally rate their bikes on low PAS under ideal conditions, but that's not necessarily reflective of the real world. I know from my use, I'll range anywhere from ~5wh/mi just casually on a flat trail (which would be 100+mi range) to 50wh/mi if I'm in traffic or riding it like a dirt-bike(which would be like 10 miles of range). Depends on the terrain and my pedaling.
For the HD / 02 - I've not used the bbs02 so I can't speak to that. But the bbshd has been nothing but reliable for me. I have an egg-rider display, so I've tuned it to my preferences regarding power output, street and offroad settings, and battery settings. The HD PAS is cadence based. The 02 is a torque sensor. Cadence is fine if you're going a relatively constant speed, it hasn't bothered me any. It feels a bit more like cruise control set on your gearing. I keep dogging Luna for their ludicrous controller but they guard it quite closely
