With mint as with many other plants
, the larger the plant
the larger the root ball. So keeping a mint trimmed back is a good idea in your situation.
I have never heard of a small mint. Most are about the same size. There is catmint, but it's not "minty". I'm not sure if catmint really is a mint.
A 6" pot, watered when almost dry, and a sunny windowsill and your mints should be OK.
BTW, spearmint grows happily in water only. Like in a clear glass vase. The water would heat up in a windowsill though.