So, you run your tanks low on water in case of possible flooding issues? Most have their tanks filled so water line is not seen by anyone. ??
No the water line is not visible. It's just not at the very top of the tank, it's down a little, but still hidden by the top molding/brace.
A lot will depend on the size of the sump and tank.
For instance, If you have a 20 gallon sump and a 55 gallon tank, you might run the sump at half, and the pump at half of that, so now only 5 gallons can be pumped from the sump, with the water level in the tank at such that 5 gallons or more can fit. You run the drains from the tank so that if the pump stops, less than 10 gallons can drain. That covers the 2 most common scenarios.
If I had to make the choice, I would let the water line show, and cover it another way, rather than know, I'm coming home to a flood someday.