Congrats on the new tanks, looks great!
I have a couple thoughts that I hope will help:
I assume you're buying your NSW from a fish store, etc.? I would very much recommend that you double check the salinity with a good refractometer, hydrometer, etc. I wouldn't assume that the water was "perfect" just because you're buying it.
If you're having RO water delivered to your door, I'm 99% sure that's RO filtered drinking water, which often has extra minerals added in for taste. This isn't the same purified water that we typically use in reef tanks, which is RODI or Reverse Osmosis with De-Ionization. An RODI system produces basically pure water, which is ideally what you want.
If you don't have an RODI system yet, I'd suggest using gallons of distilled water found at any grocery store or pharmacy.
You do need to nitrogen cycle your tank to prepare it for future livestock. As mentioned about, you'll want other add some type of a bacteria product, like Dr. Tim's One and Only, Fritz TurboStart, or MicroBacter Start, etc. These products provide the beneficial bacteria you need to process waste in your tank. In addition, you need to add a source of ammonia that can "feed" the bacteria and cause them to grow to a population that can handle your future livestock.
There's a few ways to cycle a tank, and adding some real, wet live rock from a good local fish store is a great way to go. Here's some more information on cycling your tank:
https://www.bulkreefsupply.com/cont..._4cf6yY23dGEv46lFvomv-MvwMCvw6takQ0MvtslCYhQa
I hope that help[s and good luck with your build!