Re the sinewave whilst it is expensive on its own its not really that much more expensive than another off road dynamo light and a USB charger and you get the advantage that you can run it form an external battery - its very low power as well . You couold just use it as your main light and the batteries are cheap !
On high[600 lumens*] the Beacon will draw about 800mA from the battery, or 4W. On low[ 200 lumens*], the Beacon will draw about 150mA, or 0.8W.
Even ignoring the fact you are charging the battery that is qite long run times from a £20 batery bank - think mine is 10,000 mA
I really would not want to do offroad with just a dynamo light - fine for gravel rides but anythingn technicall - unless you want to hammer it its going to be interesting
As for the rest SJS cycles are your friend with every version of dynamo product imaginable
https://www.sjscycles.co.uk/search/?term=dynamo
My rear is
https://www.sjscycles.co.uk/lighting/bu ... y-fitting/
£22 and bright enough on its own and has stand by function [ at full brightness] - I do have a nother rear light on anyway when commuting that is set to very bright flash mode.
Mine is 3 years old now as a set up and I have done zero things to it since fitted but yes its not a cheap thing to decide to do but it should last your lifetime.
If you wanted cheap for road i think you could get a set up for about £250 new - road light, rear light, dynamo hub so that sort of set up is not that much more than good light.