Electronic – Constant Current Drive for LED

You mention that you want fast switching. None of the devices will be able to do that. Any the feedback circuits internally are designed to be slow so that they don't to much incorporate noise. And in fact some of the feedback is thermal feedback. Put another way, the dominant pole is low, 100's of KHz is typically the the fastest response time. This is true whether you are using a disable pin or connecting/opening the load to the source.

The best way to fix this is that you build an external circuit that current steers between two limbs. On one limb will be your LED chain and on the other a dummy load that draws the same amount of current (and hopefully also has similar load characteristics). An example of such a circuit is a differential pair. You should be able to get 10's of ns switching time then.

The challenge with the two limbs will be that the load characteristic differences may disturb the feedback of the LM317 etc. which then reacts slowly. If you can't match the two limbs then I'd suggest building a current mirror that decouples the current output the LM317 etc. so that it only sees a constant load the mirror transistor sees the variability.

You should be able to simulate all of this in LTSPice or similar before building.

The other factors you mention above not show stoppers, so pick what you want.

Sorry, Geremy, but you've misunderstood. The module you're looking at will simply not work well with the dimmer turned down. It will ALWAYS try to drive 1400 mA through your LEDs. If the input voltage is too low (because of your dimmer) it will get very unhappy and may do strange things.

The 17 to 29 volt range just means that it will successfully drive 1400 mA through an LED string when the voltage needed to produce that current varies between 17 and 29 volts. This voltage difference could be produced by differing numbers of LEDs in a string, or using the same number of LEDs, but of different colors.