Laravel 5.3 Notification Vs Mailable
Although it is not in the documentation, as of Laravel 5.3.7, the Notifications mail channel can work with Mailable objects in addition to the notification MailMessage objects.
Therefore, you can create all your emails as Mailable objects, and if you decide to send them via Notifications, you would just have your toMail() method return the Mailable objects you've already made.
Yes, definitively, if each email layout is different, you should use Mailable
Mailable is the new way to send emails, easier than before. More customizable than Notifications.
Notification is very nice if you want to send a predefined layout in differents channel ( Mail, SMS, Slack, etc )
You can customize notifications layout, but having 1 layout by notification is going to get more difficult... it is just not the use case for notifications