IF you want it for ALL projects (I would personally advise against due to the number of emails I ended up getting, but may be different for you) then I would be selecting all of the options for the email notifications in the settings page, and then also scrolling down and selecting the task updates option for desktop notifications and all options in the project notifications section.
As the Mentions only is part of a multi option I select it as well as the other options.
I think if you just selected it then you would only receive updates on tasks assigned to you and direct messages, but by pairing it up you can receive more.
I’ve clicked the Share button and checked that I am due to receive all Status updates, Messages and Tasks added – that’s great to know!
In the settings page, I have checked that I am receiving all ‘Activity updates’ via email. I am currently only on one project so this is OK – I won’t receive too many alerts!
My worry was that ‘Mentions only’ would override the ‘Activity updates’ setting above.
By checking both, I’m hoping that I get all notifications via email. From what you’ve said, it sounds like this is the case and that – yes! – I will still get all the notifications.