If I no longer believe I need my home water softener, is unplugging it sufficient?

First thing I would do is to have the water tested or simply contact the water department and ask for an analysis report on the hardeness/softness of the water along with the mineral content of the water.

The white water deposits on your dishes are a clear sign to me at least that you have high mineral content hence hard water that you would benefit to continue to use your water softener. Or on the outside chance your dishwasher is clogged or on its way out and not rinsing the dishes as efficiently as it once did.

Seems to me if you have white spots left behind you might still want the water softner. My water softner measured my water hardness and did it’s thing based on what the water needed. Maybe your water isn’t as hard as it used to be, but it sounds like it still might be hard. You could have it tested, or if a rural water line means you are now on public water then you can ask the water company what the hardness is.

Since yours is electric, it’s true it uses some electricity, but probably very little. If you buy salt for your softner, the salt will only be used based on need if it’s measuring the softness in your water. My softner used salt very slowly, because it was just us two in the house. Although, I do think when my husband washed his cars that was softened water too, so that used a little more than the average person.

I can tell by “white” left behind and how bubbly my shampoo is, and how easy it is to wash away soap off my body in the shower.

As you probably know very hard water can damage pipes, plumbing fixtures, dishwashers, washing machines, tankless water heaters and glasswear.

Just because you are on a public water source doesn’t mean your water isn’t hard. Try using it, and see if your white deposits go away.
Don’t forget to put it through a cleaning cycle first.