An additional way to create a form is to use a
opens a form. This kind of workflow is suitable for
a simple form that feeds into a more detailed form, and
it is described in an article in our SharePoint
From the end of 2017 it is also possible to
customize a SharePoint list form with PowerApps. Just select that option in a list with the modern interface, and the list form will open in the PowerApps Studio.
This is described in our Office 365 from Scratch series.