In order to change the transactional emails in Magento 2 go to Admin Panel > Marketing > Communication > Email Templates.

Magento 2 Transaction Email Template, Email Templates

Then, choose an email template you want to edit or you can add a new one by pressing the Add New Template button.

Magento 2 Transaction Email Template, Add New Template

New Template

When you adding a new template, please choose an email template you want to based on in the Template field and press Load Template button.

Edit Template

1. Set the name of the template in the Template Name field.

2. Change Template Subject and Content as you wish.

3. Add Template Styles (optional).

Magento 2 Transaction Email Template, Load Default TemplateMagento 2 Transaction Email Template, Template Content

Once you have finished with the configurations don't forget to press the Save Template button.

Magento 2 Transaction Email Template, Save Template

If you have created a new template you need to assign it in the store configurations. As far as we have created a New Order Template in this guide we go Admin Panel > Stores >Setting > Configuration > Sales > Sales Emails (your path can be different depending on the template).

Magento 2 Transaction Email Template, Configuration

Then you need to find a template select box you are interested in, remove the checkmark Use system value and choose the template from the list.

Magento 2 Transaction Email Template, New Order Confirmation Template

After all of the configurations have been performed press the Save Config button and flush Magento caches.

Magento 2 Transaction Email Template, Save Configuration

In is way any transactional email template can be edited or translated.

1st  Step: go to Marketing > Email Templates in order to edit or add a new template.
2nd Step: go  Stores > Configuration > XYZ, find your template select box and change its value.