pasting from pages & notes

Applications are designed to copy/paste certain content on Apple's clipboard. Pages will place a bunch of Pages unique content, along with public.rtf (styled content) and public.utf-8 (plain text) content to the clipboard, and another application may only accept text and ignore the styled content. Purely up to the application designers what is cycled through Apple's clipboard. If the third-party application uses its own clipboard, then expect nothing.

Because Pages cannot export HTML (web page content), applications expected to accept that type of content from the clipboard may settle on text content or gibberish. Apple's Notes application reflects text that you type, but in reality, beneath what you see is HTML content. That is why you can copy/paste a URL link from Pages into the Notes application because Notes is designed to take the Rich Text (RTF) code for that link on the clipboard and converts it to HTML content which appears as a Notes hyperlink. It does this because Apple has a framework method for that purpose.

The Apple Mail compose window is not a word processing application and will not accept formatted content from Pages or another word processing application. The rich text presentation that you see in the Mail compose window is HTML formatting done beneath normal user access by Mail, and can only be achieved by a user through knowledgeable AppleScript and HTML/CSS programming.

For non-Apple mail recipients, you have zero control over how your email will be processed and presented, and even if you could format some aesthetic input in your Apple Mail client, there is no guarantee that is what the recipient will see.

As I already mentioned, individual applications are designed to copy and paste specific types of data to and from the Apple clipboard. This is baked into the application design and not changeable by the user.