What would you say is the main difference between External users and Internal users?
I´ve read that, for example, External users can have Survey or View permissions. Any other difference beside that? For example,
What about top buttons like Mail Merge?
If enabled, do they still have access to action buttons located at the bottom of sheet like Send Custom Email?
You may refer to this article regarding limited feature access for external users in Ragic:
(The access of most features under Tool menu can be configured through feature access settings.)
However, mail merge is a bit special that configuration is under tool menu, and there will be an action button created at lower right corner as well, which is different from all other action buttons you design from sheet design mode so that you cannot configure access for it (no matter from feature access setting or action button additional setting.)
For configuring access of send custom email action button, you will need to refer to this article instead:
(Additional settings for action buttons you can configure under sheet design mode.)