I’m using Nan, so far no constipation issues, however it still depends on individual. There is no difference between Nan Optipro and Nan Supremepro (Optipro now renamed Supremepro), but there is a difference between the HA and non HA. HA is more suitable for baby with sensitive tummy or with allergies which in your case, id recommend you to try the HA one 😊. Difference between HA and non HA: NAN OPTIPRO series - our advance formulation with highest 2’-FL and Immunity Guardians, contains OPTIPRO proteins --- i.e. Optimized Protein – proteins that are optimized in the right concentration and composition for optimized growth and immunity. NAN SUPREMEPRO H.A series - our breakthrough formulation to support immunity and beyond. It is a hypoallergenic, containing Gentle OPTIPRO®️ H.A., a unique blend of whey proteins which are partially hydrolyzed to help reduce the allergenic potential of cow's milk, together with the highest combination of DHA and ARA. Hope this clarifies.
My baby started out with similac but heard from a friend that enfamil is good. So i changed to enfamil after just the first tin of similac finished. But enfamil is giving my daughter bowel issues, poos only once in like 2 or 3 days and also the poo colour is of undesirable colour. So i changed back to similac. But recently similac is giving her red spots(heat rash) on her face very frequently, heard that similac is very heaty so i changed to S-26 gold now. Seems like it suits her way better, poos 2 or 3 times in a day and reduced heat rash. I really recommend you to try out S-26 gold :)