In a Power Apps, we can either create Canvas App or we can create Customized forms. So in which scenarios we should use Canvas App and in which scenarios we should use Cutsomized form?
When you want your users to allow to open a form in the SharePoint portal itself then you can use the "Customized Form" option and when you want your users can open the form via a link into the browser and want to hide the backend, where it is submitting the request then you can use Canvas App. I hope this helps you to decide the approach.
Canvas App should be used whenever there is UI customization. Model Driven App should be used when data is stored in table and no UI customization required
Customized form should be used when the user wants to open form in SharePoint ( example: Onclick of “New” button in SharePoint List).Canavas App should be used when user wants to open form in a separate page (Canvas App will be embedded on the Site Page)