I’m also curious if it’s possible to specify in the yml file for a template that it should not be accessible as an option. For example, don’t ever show the error template or home template as an option when creating new pages via the panel.
templates defines which templates will show up in the section and also which templates can be used when creating new pages in this section when no create option is set. With create you can limit which templates can be used to create new pages (so you only need the create option if it is different from templates.
Regarding your second question: No, there is currently no way to exclude rather then include templates. So if you want to exclude templates, you have to spell out all allowed templates.