I've killed a few peonies in pots by overwatering them. They just rotted. I definitely would back off on the watering!!

Do you mean flower buds? If so, better cut them off. A peony transplanted bare root at the time of flowering will not be able to establish a root system and flower at the same time. You should cut back some of the foliage too, and wait for the roots to regrow. If you had gotten the plant with plenty of soil around intact roots you could have let it flower.

I forgot to mention peonies DO NOT like their leaves to be wet - they get fungal diseases very easily that way.

You don't have to tie them - it's optional. My husband likes to tie the stems to prevent flopping (which he hates because they look messy) but it's not necessary.

Also if you are planning to leave the peonies in the pot for a while, say until fall planting, each peony should have its own pot because each peony will grow a LARGE root system by then. I've grown peonies putting a single 3-5 eye root in each 5-gallon pot over the summer and by fall each peony had filled up the 5 gallon pot and were spilling out the bottom drainage holes.