For Sending email with pre-populated details:
Work Order:
1. Navigate Dynamics365--> Settings --> Processes

2. Create New Process of Type Workflow for the entity Work Order

3. Choose the triggering point. In the below example, I chose on create of work order

4. Add a step for email in the workflow as below

5. Click on set properties to design the email
6. Place your cursor in the email body and use the form assistant section to choose desired parameters (pre-populating)

7. Choose desired parameter and click on Add. Then Click OK. This parameter will be added to email body as below

8. Similarly you can add other parameters. In the below, i added Service Account, Work Order number, Work Order Owner as a sample

9. Save the email. Activate the work flow.
10. When work Order is created, an email is automatically sent as follows:

Order:
1. You can repeat the same steps above with work flow created on Order entity. OR
2. You can create an email template specific to order entity and choose the parameters very similar to what we chose above.
Both the options work.