What size pot are they in now? Typically "potting up" is done only one or two pot sizes larger: eg. a 1 gallon to a 2 or 3 gallon size. Next year you may want to bump those up to a 5G size. And any well draining container potting soil will work - they'd prefer one with an acidic base if possible - bark fines, peat, etc. (and skip any lime). If these are intended to be long term container plantings, something like a half whiskey barrel may be the ultimate size to shoot for - most mac's get pretty large. Root pruning and refreshing the potting mix periodically will be called for for permanent container plants.

Is there a reason you choose not to plant these in the ground? Florist hydrangeas should transition to the landscape relatively easily in your area and they'd be much happier in the ground.

Primary reason for pots vs ground, is that I have virtually NO shaded areas I have no big trees on my property (and the area that I do have with some shade is already filled up with hydrangeas :)

I do have shade/filtered sun on my deck up next to the house, so they will be there for now. I'm also working on a bed on the East side of the house, that could work for them. As soon as I have it ready, then I can put at least half of them there. I just wanted to get them into something that would be better for them either for this year or even for the short term. They also btw...had tags on them, most were called Fireflight and one was labeled Mathilda gutges, so we will see if they are what they say they are. I googled fireflight and could not find any pictures.