I wanted to know what will happen to my email id after refreshing my partial copy sandbox. I also want to know if usernames will be same as production or not?
UserName will append the sandbox name. If your sandbox name is "uat" and your username in prod is email@example.com then the refreshed sandbox username would be firstname.lastname@example.org
In case of email, it makes email invalid. eg if your email in live was email@example.com after refresh in sandbox it will make it as firstname.lastname@example.org.