Just wanted to share that I have achieved this by overriding the default controllers provided by node_modules\strapi-plugin-users-permissions\controllers\Auth.js.
I copied the file to extensions\users-permissions\controllers\Auth.js. Within each controller (forgotPassword, register, sendEmailConfirmation) I fetched the Employee (my collection in strapi) using email and check the employee’s preferred language. Based on that I send the customized email content (En or Fr).
Thank you team for your response!