You can for sure dim that light down under 200 watts without issue. That said, I don't own the diablo 200 kit but have a few meanwell xlg-xxx-a drivers that I run well below their max output with different boards/strips and no issues.Glad to see that Padawan still realizes that the O.P. (me) is still here! I must admit; this thread has turned into T.M.I. (too much information), though I still find it informative. Here is what I've got so far:
1. The Diablo 200 is a killer unit, albeit, with some "controversy" over the dimmability. That is fixable or controllable, one way or another.
2. Replacing the driver (for the "correct" model) would solve the controversy - best choice!
I don't have a tent, I have a purpose built growbox. It is "modular" so I can add a section, or drop a section, and make it any height I want. I'm thinking 6 ft. (or 2 meters) should be enough. What is the current RIU Discount code for HLG, I like to save money? That very light you suggest was my 2nd choice overall, I just thought that the Diablo 200 had a little extra kick. Plus a little more "Red spectrum" light.
Like others said earlier, there's a small plug on the bottom of the driver with allows you access to a "screw" that will adjust the amount of current allowed to the boards. In turn, the driver will adjust the voltage down to match what the leds require to run at said current. It will essentially give the same result as people who have knob style dimmers.
I would recommend getting a kill-a-watt wall meter and you can use that when adjusting to get into whatever sweet spot you want it at.
That is just my basic understanding on the xlg series drivers. I am no expert by any means so hopefully someone can clean try to re-hash this out for you. @shimbob has seemed to be able to explain this best imo. Sorry for the semi rant, just found myself confused as well to what was actually being said.