How cold does it get in Winter, and will you be able to protect the plants if it gets too cold?

There are many varieties that are possibilities.

Kt

I could overwinter them indoors while small, but once they got big enough I would have to leave them outdoors year-round. I live in the city, which is officially zone 7a but the lowest temperature I've measured in my yard in 7 years is 6 degrees and single-digit temperatures are uncommon. I think that probably limits me to some of the Phyllostachys species (bissetii? nigra?) or other fairly hardy species.

I would recommend planting a clumper since they don't get rootbound as fast and they do better in pots than runners.

If the plants get too tall, you can top them to any height you want so you could still bring them indoors if needed.

Look into some of the Bambusa multiplexes. They remain small in pots and grow very dense.

Bambusa mutiplex 'Fernleaf' might be a nice one for example.

Kt