The data sheets are so hard to read if you don't know all the stuff in them
All transistors I can find seams to work with really high voltages or with very low amps.
If a transistor is rated at 40-50v can I still use it on the Arduino board that is using 5v and LEDs at 3v?
Don't confuse the maximum voltages with the working voltage, typically a transistor might have a collector emitter breakdown voltage of 60V but you wouldn't use it at this voltage, it would be fine for using up to 30V or so.
and dies in the process, right?