I've used salt and increased heat to clear Ich in my QT tanks, which generally have plants (as they are also grow-out for young plant or divisions) without problems. I use 1 teaspoon per gallon actual volume, temp 82-85F, hold at least 10 days past last visible symptoms, then dilute out out salt with partials and reduce temp slowly back to normal.
As for light brackish on a chronic basis, some plants will suffer from the salt and high pH. Val, some swords, Crinums, Java Moss and Java Fern, a number of others will handle very light brackish - say no more than 1.003 specific gravity. Beyong that it gets harder.
HTH