To be honest its going to be an 'everyones different' answer. As far as I know, You cant overdose on probiotics, certainly not the natural ones as they only contain cultures which should be present anyway. Having an 'excess' would lead to excretion through bowel movement.
That said there is very little evidence that probiotics help anyway, and for the price a lot of doctors are against them (I take symprove even though my doc is certain im wasting my money).
VSL is the one that supposedly has some testing in J-Pouch, so I would probally take that one and forget the florastor. If pouchitis comes back its sounds fairly stubborn, not sure a few more strains of probiotic would help anyway. Or you could do the other way round, take both for like 6 months, then end the florastor..if Pouchitis comes straight back you know.
Just be aware that probiotics can interefere with other meds, and can course an increase in allergies in some people, (hence everyones different). Personally id try and keep the regime as simple as possible with VSL and consider dietary changes if necessary.