I’d be wary of putting it right above the laser, for a few reason.
1) Heat rises. No need to put electronics right on top of a hot laser. Though, did you buy the additional fan to use a “semi-air-assist” to blow smoke down and away from the laser? That might move most of the heat away too. I’m about to hook mine up tonight or tomorrow (just came in the mail) and will see how hot it gets just above that fan. I imagine not much if the fan is blowing down towards the workpiece.
2) Z stability. This is pretty stable, but I always worry about it. Are you also going to use a router or printer head on it? How would you get the laser driver off and unplugged to do a tool change? I’m happy that the laser is nice and light and doesn’t cut laterally on the surface to create twisting tension…but I wouldn’t add a fraction of an ounce to the Z axis just out of pure OCD about that kind of stuff. Particularly since there’s not a whole lot of easy ways to adjust Z straightness outside of the tool mounts.
I’ve read about adding the fan to whatever power the driver fan is on, but haven’t checked it out. That’s my “plan” for researching today.
The pic on the JTech site I think assumes a real “power supply” source other than the laptop style plug that I got here. They have additional fans and LEDs plugged into that. If you’re using a more dedicated power supply like that, I’d think having it on there would ensure not drawing too much power from the driver board (I’m not an electrician, so I know nothing of this, just speculation).