Probably a very individual thing...

Salt is probably needed when there's weakness, muscle cramps and low blood pressure and potassium when there's fatigue, muscle weakness/flabbiness, constipation and fluid retention.  For me, potassium is "it" most of the time.  I'm sure I've had adrenal problems most of my life, I was diagnosed hypoglycemic 24 years ago and now I'm probably insulin resistant to some degree.  Almost 9 years ago I was also diagnosed with hypothyroidism, which I'm sure was brought on by stress; as I learned about adrenal fatigue I realized I'd had all the symptoms for a good while and they only got worse after treatment.  Incidentally, potassium absorption can be impaired in most people with hypothyroidism.

 I started taking OTC potassium tabs (usually 6 or more at a time) after reading in a very old nutrition book (Let's Get Well by Adelle Davis) that potassium helped control hypoglycemia symptoms and they do help me.  Ms. Davis really recommended potassium chloride since the tablets have very little potassium in them so I have kept a bottle of it in the house for years too.  I've mixed it with salt in a shaker for when I need extra "salt" in my food and have taken it dissolved in water when very fatigued or when/if my blood pressure goes up, usually brings it down quickly making me feel much better, it also acts as a diuretic when I have fluid retention (very common for a lot of us women...) which is usually accompanied by debilitating fatigue and mental depression.   But for about a year now I've been taking mostly potassium citrate tablets, I was having very acid urine and gout like pain in my big toes and during a search online read it  helps neutralize  excess acid in the body, it really works but I do have to spread it out during the day (when I take it, I don't really do it every single day...)  because most forms of potassium can be a little hard on the stomach.  I also have taken (among other things...) magnesium daily because it helps potassium assimilation.