Even faster – open the Print dialog. Then click the PDF dialog. At the bottom of that dialog choose Edit Menu…. You’ll see a list of all the PDF destinations. Press the + sign. A folder dialog will open where you navigate to Applications > Notes and press Open. That will add Notes as a PDF destination in every print dialog. This is a one-tine set up, and you can then print email as PDFs directly from Mail.
(I love this macOS feature – I currently have 45 destinations – apps, folders, drives, etc. – defined in the Print dialog as PDF destinations. Major time saver.)
You can also add a keyboard shortcut for that destination. So you’d only need to hit Command-P to bring up the Print dialog in Mail, then hit your preferred shortcut for that new PDF-to-Notes destination.
FWIW when I moved from Evernote I initially had Notes import all the PDFs. Notes became very slow. After a few weeks I moved all the PDFs out of Notes. There really wasn’t any benefit to having them there as Finder and Files (on iOS) do admirable jobs searching them. Notes perked right back up after I moved them.