I have ordered a hub dynamo as part of the build so have that covered.
I'm just confused by the light options.
It's an SP hub.
There are lots of lights out there, depends in part on how much you want to spend. I am in USA so I do not know what the prices are like where you are. But they are getting better every year.
The B&M website has sample light beam patterns for their different lights. Most of their lights, if you click on the light you can see a sample beam in a small photo. If you right click on that sample beam and then select open in a new tab or window you can see a much larger example of that light beam.
https://www.bumm.de/en/products/dynamo-scheinwerfer.htmlB&M also makes some lights for e-bikes, make sure you do not accidently order a light for one of those.
And choice depends somewhat on what you want the light for. If for road riding, you want a light with a good wide flat beam that does not waste much light by shining it above the horizon. But if you are mostly riding on gravel or up and down trails, a light with a flashlight circular beam might work better.
Supernova headlamps I believe have to be used with the same brand taillights, but I could be wrong on that.
Other brands, you can mix one headline brand with a different taillight.
Dyno powered taillights are always on, do not flash. I often use flashing taillights in daytime, so I consider my battery powered taillight to be my primary taillight, and the dyno powered taillight to be secondary. I think I went for about four years with a dyno powered headiamp before I even bought my first dyno powered taillight.
SP hub is not grounded to the fork, so you do not have to worry about making sure that you have the right wires connected to the right wires. Shimano hubs are grounded to the fork, and if your headlamp is also grounded to the fork then you have to make sure your wires are connected correctly for it to work.
You wire the headlamp to the dynohub. And you wire the taillight to the headlight, that way the headlight switch controls both front and back lights. The taillights usually are not protected for overvoltage, they rely on the headlamp for that so you can damage your taillight if you wire it to the hub, that is another reason to wire it to the headlamp.
On a different forum I documented how I wired up my randonneuring bike lighting, that link is at:
https://www.bikeforums.net/electronics-lighting-gadgets/1228845-wiring-up-dyno-powered-lighting-system-usb-charger.htmlGood luck figuring this stuff out.