Yes, you are right, catts, oncidium types encyclia.... like more light than phals.
I have several of the 'mini-greenhouses'. And have added fluorescence T5 lights to them. HPS generate heat, I think. So the plastic material of the mgh might not work well with HPS. Though you don't have to use the plastic cover of the mini-greenhouse and just make modular shelving out of it. I have it both ways. My outside shelving is made of leftover mini-greenhouse parts. And I have 3 mgh's with the covers on.