I’ve only been low carb for about 2 weeks so take this with a grain of salt…
Pre-keto I was supplementing salt heavily. I was having weird chest pains and muscle aches and found that adding pinches of Himalayan sea salt to my water (reverse osmosis) helped. I was also drinking Sole I’m the morning (basically a tsp of brine in a cup of water). My diet was decently good, fairly low carb and subsequently low sodium. All this is said, if I messed up the amounts and ended up in excess I had other weird symptoms (tingling extremeties, heart racing).
Queue Keto. I’m still in the adaptation phase, however much of my water purging has slowed down. During the great purge my salt supplementing proceedure continued and I found I avoided much of the Keto flu. What has been weird for me lately is that now that I’m not purging water so much that supplementing feels waaaay different. I was finding that each time I put 2-3 pinches of salt in 1 litre of water that I could feel the effects immediately and to a greater degree. It actually felt, to me, to be too much. My chest felt abit tighter and my extremities did the tingley thing again.
So, I’ve been dialing back on the salt and now feel much better. I will still be treating salt as a supplement but I need to find my “new normal” after I adapt. It may be that because my body is not squirrling away salt in my stored fluids that I can’t spike my system with too much salt in one go, I need to gradually eat salt over a day. Dunno, still learning 
TLDR: I use to supplement salt pre-keto. During early adaptation it helped, once I began my adaptation I found I could handle less in spikes. YMMV.