Can't really see all the details, but I think Cylindropuntia imbricata?

Of the 100s and 100s of babies, I saved these bulbils - just put the end slightly in the ground and let it do its thing. I tried to get some healthy replacements for the plant that bloomed, and I tried to get any with unusual marking - quite heavily variegated, all green, bi-color. And I potted up over 50 of them to root. (and there's another flat that is missing) The albino bulbils didn't grow, as expected. Highly variegated plants were much slower to grow and they have been slowly reverting to marginated form. The highly variegated coloring is not stable in most cases. I gave a lot of babies to friends, many to the local parks, and we posted a notice on Next Door for folks to come get the babies if they wanted them. These are some of the 20+ babies that were around the bottom of the plant. They are pretty large and my neighbors laid claim to most of those! LOL

Can you post a photo pls?

That cultivar would not be my first choice for a containerized hydrangea. It just wants to grow too large and unless you consistently up-pot or root prune, you risk the shrub becoming rootbound rapidly and with somewhat stunted growth. This cultivar is recognized as having the largest panicles/flowerheads of all the paniculatas. To encourage larger (but fewer) flowerheads, in late winter or early spring thin to 7-10 of the strongest primary shoots. But be aware the weight of the very large panicles may bend down the stems.