If you have two languages you need emails in, the most common approach is to implement a filter function for the second version of the email based on the language being used.
There is a main filter hook for all emails (and content can be filtered using this hook) or alternatively, there is an email hook for the content and subject line for each email type (new registration, moderated registration, approval, password reset, admin notify). See the hooks under “Email” in the list of hooks here:
https://rocketgeek.com/plugins/wp-members/docs/filter-hooks/
