Yes you can use any NPN transistor that can handle more than 2 Amps. This kind of LED draw less than 2 Amps. Power transistors can handle it happily. It handles a 100W TV set and LED is about 20W.so I could use any general purpose NPN? like a 2N3904?
I'd need something much larger for dimming this LED though, I think. It's pulling more than 1A when it runs.
It is quite simple dude
Transistor is operating in emitter follower mode. Output voltages would be equal to base voltage. Output current also depends upon the base current. If you feel deficiency of current just replace the pot with a lower value (e.g. 1k or 2k etc.).