your wallet files are not removed when you uninstall electrum.
anyway what you are proposing is not cold storage. if you are going to do it this way you might as well leave the seeded wallet in place and not bother with a watch-only setup.
what if I delete them manually? yeeh I know it's not a cold storage but trying my best I have cleaned my laptop. I can use live Ubuntu on a USB drive to make it as a cold storage?