Each strain has a specific spot in the GI tract, they build their little house in a spot they are comfortable in. Bacteria love to do things in group, they are not happy on their own, they do everything they can to be in the same spot, many create biofilms, it makes them stick together. Mucosa layer moves also, mucosa does not sit still, it moves all the time in the body as a form of defense mechanism, if it say still bacteria would take it over, so they go somewhere they are happy with. Probiotics have specific spots on interest. (invasive bacteria creating disease do the same thing, the place of lesion and skip lesion in the intestine are related to "the nature of the beast" bacteria are predisposed to go somewhere in the body)
(this is one of the arguments for bacterial involvement in crohn, if it was autoimmune or non-pathogen related, you would have inflammation everywhere, that doesn't happen with crohn, it's almost always terminal ileum involvement and skip lesions are almost always in the same spot)
As a general rule:
All the ones I know called lacto-something..take up spots in the small GI tract.
All the ones with "bifi" in them reside in the colon.
As for which are good, I talk to someone a lot who does research on that, and to be fair they have no clue what is good, he recommends just to take ones you are comfortable with at this point as long as you pick a kind that use the small intestine.
(they are looking at types that increase butyrate, there are some that do that, I have taken that type, but I can't say it is good or not, I don't really know how much it helps)
(reason for the butyrate is because for one they see butyrate is less in ppl with CD and second, butyrate has an effect on IL-10, IL-10 is a super strong anti-inflammatory in our body)
(argument against SCD diet is butyrate, SCD is way too short on SCFA (short chain fatty acids), most important one is butyrate, I am not a fan of SCD at all)