When you disable Personalized email replies, the agent's name is hidden in the Sender field of the email.
When Personalized email replies is enabled, the email that end user receives is shown as below. Agent name is shown in Sender field.
When Personalized email replies is disabled, the email that end user receives is shown as below. Agent name is NOT shown in Sender field.
However, even if the above is disabled, the agent name in the body of the email (see below) will still be displayed. This name can be changed by using Alias in each agent profile page.
When you enter like this in Alias field...
the name appear in the body of the email received by the end user will look like this. No agent name is displayed.
For more details about agent alias, read Adding an agent alias.