Check my other replies for the brands. I don't think it matters as long as the quality is assured. I had known about probiotics for decades but never realized how fundamental they were to overall health. When I was going through this I just thought about my symptoms and took a hail Mary with this treatment. Bowel movements were extremely stressful at that stage. I was depriving myself of anything solid to alleviate the issues but overall I was not getting better. Previous to that I was doing fine, or so I thought. I never ate out, rarely ate meat or anything processed.
You will know when it's restored, you can even eat garbage (meat, processed foods) and your gut will process it and move on. You should be able to notice the subtle changes when you eat something that does not digest readily. It's not the acid and body mechanics, it's mostly the bacteria giving you life by breaking down nutrients and solids. Feed it what it needs and it will sustain itself. Raw and fermented vegetables.