I think it could have a preventative/supportive role. If you’re not producing enough stomach acid, then a lot of crap can get into your small intestines, and candida itself isn’t as inhibited as it should be from forming colonies there. Stomach acid neutralises most of the dangerous stuff in what you eat, leads to a lot of inhospitable stuff being released in the small intestines, and prevents undigested food reaching the bowels where candida and other bag bugs can take advantage of it. Clearly, if your stomach acid is low, it’s something you need to address.
As for side-effects, gastritis is the obvious one. Taking DGL licorice and marshmallow root before the HCl tablets should help to provide a protective coating in the stomach and sooth mucosal inflammation. You want to start with a small amount and test to see if you get a warm feeling in your stomach. If you don’t, you keep gradually increasing until you do, and then reduce by 1-2 tablets. Supposedly, your stomach will start contributing more of its own acid, so you can continue to reduce.
If you have a history of antacid/PPI use or H. pylori overgrowth, it’s well worth a shot. Let us know how it goes.