Wow, a Nightsun? Those things are OLD.
I know, I have one. The 30w rating was with both beams on, and IIRC, the battery lasted ~45 minutes on HI. That battery pack was also a low-output NiCad setup, that weighed about 3 lbs and took up a water bottle cage.

Some of them have been upgraded, over the years, mine included, to MR-16 LED bulbs, and Lithium Ion batteries, usually re-purposed from 12v power tools.
If you already have a set (which you don't yet) and some 12v battery packs, and like to tinker, it can be a neat conversion, but if you're starting from scratch, it'll be far less expensive and more effective to get a modern unit.

As above, it's not watts, it's Lumens that determine the 'brightness' of a light. 350-500 is more than enough for you to see by, especially if you're operating in an area that has other light sources (streetlights) Unless you're running a 5" lens reflector, oncoming traffic will never mistake you for a motorcycle, no matter how bright your light is.

WRT tail lights, I wouldn't pattern mine off of a motorcycle tail light. Stock motorcycle tail lights are notoriously small and low powered to begin with. You also don't want to try to look like a motorcycle from the rear, and invite traffic to come up behind you at speed.
For a bicycle, you want something to call attention to yourself, that you're not a motor vehicle; Blinking tail lights will alert overtaking traffic that you're a bicycle as soon as they see you, long before you're in range of their headlights. Most good tail lights have pulse or strobe settings along with a steady hi and lo.