For potassium there is normally no need for supplements. It is enough to eat more vegetables. The general population, especially in USA, is likely to eat not enough vegetables, so they may have low potassium because of that.
Nevertheless there are old people who may eliminate too easy the potassium from the body. Those at risk to have this are typically old women who have taken during many years medication for high blood pressure. For old men taking medication for high blood pressure, the risks also exist, but they are much lower than for women.
Those belonging to this risk group would better have a few times per year a blood test for electrolytes, especially for the sodium and the potassium concentrations in blood.
Only when the potassium concentration in blood is found to be low even with a healthy diet rich in vegetables, then potassium supplements are needed.
If potassium supplements are taken, chloride is not a good choice, because it provides excess chloride that is not useful. The salt eaten provides enough chloride. Better supplements are based on organic salts of potassium, e.g. lactate or citrate, which provide only potassium without anything else that might have unintended effects.
Source: my mother belonged to this risk group. She developed hyponatremia & hypokalemia and it was a very tough job to determine appropriate doses per day of salt and potassium supplements while maintaining the blood pressure at acceptable levels with only small doses of blood pressure medication, as that increased the rate of elimination for sodium & potassium.