Sean, the 2k clear is what Troy used and it is an actual 2 part paint. The can has a reservoir in the bottom of it that contains the hardener/catalyst. You use the special cap from the can to puncture the reservoir and release the catalyst into the paint. Once the reservoir has been punctured you have something like 12 hours to use the can. This is really good stuff, I have gotten to where I keep two cans in my shop at all times.
On the lacquer vs. enamel, well it comes down to preference really. Lacquer to me is thicker, levels better, and takes less overall work. It also gives you a real warm tone of color. I find lacquer to work better for a vintage look and using dark or warm colors. Enamel is easier to use if you are doing effects or multilayer paint jobs. Also enamel gives you a much glossier effect when done right. For example, let say you wanted a solid black bike, gloss, no fancy stuff...well then I would go with lacquer. If you were to use enamel you could get a real nice shiny gloss black, but they would look different. The best way I can explain this it the finish just has a different luster, like polished nickel vs. chrome. The lacquer will give you a warm ambient glow like the polished nickel will, while the enamel with loads of clear will give you the pop of chrome.
I have never used the 2k clear on lacquer, so I am not sure what the result would be, but the 2k works great on enamel. The real trick is you have to allow the paint to fully gas out before using the 2k on it. I like for it to sit 7 days in a warmish dry area (70-80 degrees).