remember that 2 lights are ALWAYS better than one, even if you sacrifice brightness.
as said above, no light is capable of 30k lumen for 2 hours with that small of a battery pack.
The light output profile will look like it's little brother
We Test Lights | VL15000P Test and Review
It will be less obvious on lower brightness settings, but they are certainly a bit optimistic with their claims. In video with high quality cameras, even gopro's, you aren't going to notice the dropoff. I had a fairly well known diver buddy of mine who is big into photography/videography swear they didn't do it until he he took interval shots on his dslr in manual mode and then he saw it. It's enough that if you want to do professional video work with them, I would probably avoid them, but for gopro work in a cave, they're perfectly fine. My biggest axe to grind is the false advertising they are doing. As long as you are fully aware that your 30k lumen is really going to be like a 25k lumen at the beginning, and probably a 10-15k light after an hour, then you're ok.
If I were looking, I'd probably go with a pair of these
1-V30WS_UV Video Light – ANO Online Shop
or these
V70WS Video Light – ANO Online Shop
I'm not a huge fan of the ring switches, but they work quite well and the charger dock is super nice instead of having to disassemble each night. A buddy has a pair of these lights and is quite happy with them. Another has the 2300 spot, and 6000 lumen video canister light which are quite nice. For budget lights, I'd have no problem with them