Although you can define multiple quick create forms, only one quick create form can be used by everyone. The form everyone will use is set using the form order. Quick create forms cannot be assigned to security roles and they do not provide the capability for the user to switch forms.
Verify the version you would like to restore is not older than six months. At the current time, only app versions less than six months old can be restored.
It totally depends on your plugin style: In case for early-bound, I like using LINQ because it’s strongly typed and It helps development speed. Certain benchmark test have proved that Fetchxml is slightly faster than QueryExpression.
As per Microsoft official docs, there is no visible performance difference but just a personal preference of the developer.