I am about to get a 12 week old Cardigan Welsh Corgi male. Would the micro prong collar be correct for this breed, and then just add prongs as he grows?

I would think for a Cardi a small link collar would be the best fit as an adult. The micro would be ok for a young puppy, but Cardigans are not really that small, and their fur is pretty thick. We have Pembroke Welsh Corgis and if we need a prong, I use the small link and I believe Pembrokes tend to be a bit smaller than Cardigans.