1.024. I use local NSW and that’s generally what it is where I collect. I keep Reef Crystals to supplement if I ever need to. I also top off every single day manually (I have a nano ATO for vacations).
1.026, if it goes to 1.027 I don't stress at all over it and just take a few liters of water out so more RO goes in. My checks are temperature compensated with a Hanna unit.
I always keep it at 35ppm going higher or lower is not good at all. Rule of thumb for me is always keep your levels as close as possible to NSL. And stable as possible. You will get the best growth and color for your corals. And your fish will be happy to.