The biggest change will be in "morphology" - plant shape and development.
Going to a low power light will reduce growth but the advantages of using a blue heavy light are that plants grown in a classical "veg" light will tend to be short and compact with lots of branches and small leaves and very short internodal distance which allows buds to "stack". Blue photons in inhibit cell expansion so plants will tend to grow out instead of up. That's why "back in the day", cannabis was grown with veg lights and then flower lights.
HPS is a classic flower light — lots and lots of red and just enough blue to stop plants from growing abnormally (yeh, you need at least 4% blue or cannabis gets weird).
My first modern LED was a Mars SP 3000. It worked fine but, as I learned about grow lighting, I decided to go with a Growcraft veg light and then one of their flower lights. The plant below is an example of a plant that was vegged with a veg light. Full disclosure - it was also topped and LST'd but the blue light gave me a lot of branches and leaves and then the flower light made everything fill out.
If you don't use a light that has blue in it in veg, you'll get very tall plants and they can be a PITA to work with and to harvest.
830 watts is a bucket load of input power. I'd recommend sending Amazon $32 and they'll send you back a Uni-T light meter. I've attached a copy of a document I wrote about converting lux to PPFD and it will help you set your light levels.
