I just muscle tested positive today for threelac and primal defense while threelac does have probiotic in it. It is not the type that will inhabit your gut. The primal defense has many strains that will do this. There is another one that sounded good to me I think it was called biok plus. Someone I think named Nancy posted about it recently. I will look for that info and try to get back to you on it.
As for threelac and die off I personally have not had much and I am up to the 5 packs a day for 30 days before I scale back. With both the threelac and the primal defense you can slowly build up to the higher doses.
Good luck to you I know it is so confusing and hard to decide what is the right thing. I myself have a cabinet full of stuff I have bought that just wasn't the right thing for me.