It can have it's own members area look if you setup a membership for it. It will have it's own look, however, the members area would share the domain from the primary site that the piggyback is attached to.
If you add the product into your current software the members area will look the same by default. However, with a Tool Truck you are able to modify it so each membership has it's own completely unique look. You have full html and php control for that membership to customize it however you want.
Yes, things do change. A landing page does not have the code for sending the form, so any forms on the page may not send and/or may not be setup properly if the page is not marked as a capture page.
Yes, you can edit the contents of any page in your members area through the file manager
From the file manager go to the uploads/adminpages folder (there is a quick link in the top right).
There you will see html versions of all the php pages in your system's members area which you can edit to change the appearance of the php pages in your software members area.
, there is a section called "Manage Email Templates" where you can create email templates to use multiple times.
Once you've added an email template, you can use it by clicking the red email icon in the editor.