Yes I believe I've watched that video but he doesn't seem to talk about hardness, mostly PH (or I missed it, which is entirely possible.)
The tank is setup and running and has been doing so for a few weeks. My local fish store doesn't have any puffers in stock yet so we are just patiently waiting and trying to make the new tank as appropriate as possible. I'm wondering now if perhaps my KH is okay but the GH is a bit soft and I should be up in the 70-140ppm for GH. It would easy enough to adjust the softener to reach that but I just can't seem to find consistent numbers anywhere.