There are a range of ways to have multiple distro’s on a single USB if they fit, but really, this is something you should just try for yourself. I did the same and ended up trying all sorts. Icurrently have a USB drive with Mint and Puppy. Mint for when I want to have a full distro and Puppy for everything else. Me personally, I find Puppy the simplest , fastest and easiest on any machine without buckefsfull of RAM. It even works on my really old laptop with 1GB.