The add-on allows you to specify if an account is required to register on each specific event so yes, it can be optional.
There is a feature within the add-on that checks the registration values for existing accounts and stops the registration if it finds a WP User account matching those details by default but it can be disabled with a snippet, like the second function shown here:
The support post ‘Can customers create an account?’ is closed to new replies.
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Support forum for Event Espresso 3 and Event Espresso 4.