I wouldn't normally recommend this but I've seen photos by others who have kept them in large containers with trellises for support. (the larger the better I would think) You can contain the size by cutting them back in late summer after blooms are finished. (when you finally get blooms) They would look great on your new patio or beside the stairs. Again, it's not ideal, but since you already have them, what have you got to lose?...yg

They're lovely. You can prune it to your heart's content. Let it bloom and then prune it.

They bloom in mid spring in the north. The remaining leaves are very attractive. It's perfect for a porch. They need a lot of sun, they're not like other hydrangeas. The ones I've planted in the shade do not bloom...and we're talking 10 years. They're also very slow growers so I can't imagine the pruning would be much exercise.

Keep them.

Return them to the place where you bought them for refund or store credit depending on a store's policy.
IMO, it doesn't make any sence to put camel thru the needle' hole.
Intentional planting something that will outgrow given space in a very short order will not do any good neither to you nor to the plant.
All IMHO.

If you have the time, why not build a simple pergola for it to climb? I know that arbors are readily available for purchase but can be expensive - but this, too, would work beautifully. My DH built a simple pergola for a trumpet vine and it is perfect for climbing hydrangea too.

Westy