I own both the Metro Pro 1100 and the Hotshot 150 and have had both for about two years. I do not know about charging it with a usb powerpack--have not tried that. That said, I just plugged it into my laptop for charging and turned on the light. Every mode works perfectly while it is charging. So, not sure where you got that information that you can't use the light while it's charging. Seems to work just fine. But I am no kind of battery expert, so cannot say how it might do with some other type of battery power source.
For the most part, I run mine in the 1100 mode exclusively. I ride every day and my standard, short ride is about 85 minutes long. I have not had the Pro 1100 go dark on me yet, so I am getting more than the claimed 60 minutes in Boost (1100 l) mode. Not sure if there is something wrong with my light, or if the company just is being conservative in its claims.
Not familiar with L&M, so can't comment on them. Will def check them out. But, if you are looking to add another headlight, and I am one who recommends that for most of us, I would urge you to look into the Ceco F1000. It is a 1000-lumen source that is quite a bit brighter than the Pro 1100, is in a small, light chassis, and has a better mount system than the Cygolite in my opinion. Super easy to use. I think it's a better light, though you can't really go wrong with the Pro 1100 either. Another thing about the Ceco is that it is only 40 bucks on amazon. A steal, really.
As I have pointed out freely elsewhere on this site, I am a safety freak. I've not been to Nebraska, so I can't comment on what it is like there. But here, west of the Cascades, in the Pacific Northwest, the never-ending rain and long, long hours of total darkness in the winter make visibility and safety a massive issue for us. As a result, I now run three headlights simultaneously during these months: The Pro 1100 on my helmet; the Ceco F1000 on my left bar: And the ridiculously awesome Cygolite Trion 1300, 3-LED source on my right bar. I can see pretty darn well in even the worst rain on the blackest nights. I can see debris. I can see the pavement surface defects. I can see. So, I strongly recommend that you consider adding another light if it is at all with in the budget. I think you'll be amazed what another source will do for your visibility.