Choosing probiotics can be a confusing and complicated task.  One excellent and recent study looked at which probiotic strains are the most effective for IBS (irritable bowel syndrome).  This was a systematic review and network meta-analysis of 43 randomized controlled trials (RCT's).  They found that a spore probiotic called bacillus coagulans was the most effective at improving symptoms relief rate, global symptoms, abdominal pain, bloating and straining scores.
Spore probiotic Bacillus Subtilis was used in a phase 2 NIH funded clinical trial to reduce staph bacteria in the gut AND nose:
https://www.nih.gov/news-events/nih-research-matters/probiotic-blocks-staph-bacteria-colonizing-people
Here are studies specifically looking at Megasporebiotic:
https://coe.unt.edu/news/unt-research-shows-benefits-spore-based-probiotic-supplements
https://pubmed.ncbi.nlm.nih.gov/36111808/
https://pubmed.ncbi.nlm.nih.gov/32120994/
https://pubmed.ncbi.nlm.nih.gov/31438618/
https://pubmed.ncbi.nlm.nih.gov/36769543/