What you have are called herbaceous peonies because they have soft stems. There is no problems growing them in a pot temporarily. For long term like more than 3 years, some sources say that growing herbaceous in pots can lead to peony death when they get big and the roots strangle themselves due to lack of space. When you see a decline in peonies growth or performance, it is best to take them out of the pots and check to see what happens to the roots underneath. Other than that, just make sure that your pots do not get waterlogged and have very well drained soil. After flowering, you can place the pots in partilal shade preferably afternoon so the roots don't get fried.

Right now my local Costco has lots of budded peonies in 5 gallon containers that are selling fast. Unfortunately they are grossly root bound, and no matter how cheap they are, a poor value. Most of the buyers are doing peony for the first time as peony are not a popular plant here. No wonder so many local gardeners tell me they can't grow peonies. It is much better to start with a good division planted in the right place with properly prepared soil, than to try and save a weak plant kept alive in a container with chemicals to make a sale. Al

If the buds are still just appearing, it may be OK to get those containers and transplant them.

I was just thinking today about how much lack of gardening info we have as a general population. We have moved away from even having backyard gardens. Youtube videos instructing us about how to plant stuff are saying "get soil, put the plant in". We didn't even know that much, I guess.

So I think if a store presents a plant and people buy it because of how it looks or the future prospect of how it looks, I can't fault the store if people didn't research more about how to take care of their plant.

We can certainly fault the store for other stuff, including the first few days after the sale, but not about the plant a few weeks after the consumer has gotten it home.

I'm growing up to 2-3 of them in a pot if they are smaller, but once they start getting root bound and stressing for water, they will need to either be divided or moved into bigger pots.

The first couple seasons should generally be fine.