please do not put your actual installed system (read/write) on a flash drive. linux will let you. it will happily install to the flash drive and it will happily boot up. it will let you log in after just a few minutes. plus ten seconds every time you click something.
please don’t use flash drives for anything other than installation media unless you’re using a distro that’s specifically designed to be installed portably and doesn’t do a ton of disk I/O.