- They are not under
Note, but instead
Notes and attachments are for attachments and the "old" note records. Enhanced notes have their own related list (called "Notes").
There's the Considerations for Setting up Notes where below point is taken from the doc and answers your 2nd question:
To set up Notes, add the Notes related list to all relevant page layouts and enable Notes.
This knowledge article also mentions the same about the "new" notes being managed in its own related list while the "legacy" notes being in the "notes & attachments" related list.
Add the Notes Related List to Page Layouts while continuing to maintain the 'Notes & Attachments' related list on layouts to allow users to view and reference legacy notes added to records prior to enabling enhanced notes.
In Lightning, the 'New Note' button is not available in the 'Notes & Attachments' related list. Users may only create enhanced notes via the 'New' button in the Notes related list.
Now, the reason for the need to switch related lists is due to, as you noted, the fact they're stored in a different manner. They no longer are within the Note object.
"Enhanced Notes" are stored under ContentNote.
Represents a note created with the enhanced note taking tool, released in Winter ‘16. This object is available in API version 32.0 and later.
To query, you can work directly against it
SELECT Id FROM ContentNote
However, it's important to spot this in the documentation
ContentNote is built on ContentVersion, and so it has many of the same usages.
This allows you to actually query against ContentVersion, which may have more information, using the
SNOTE value for the
SELECT Id FROM ContentVersion WHERE FileType = 'SNOTE