Your Evernote system is very similar to an analogue (good old-fashioned pen and paper!) system I use called Bullet Journaling, although it puts more priority on collecting tasks, ideas or thoughts according to category/project in ‘collections’. http://bulletjournal.com/ for more info.
Anyway, thanks for the read! My day job doesn’t require that level of task prioritisation (well, it does but unfortunately I’m forced to do it on a scrappy bit of paper and mentally prioritise as I go along) but one day I may very well give your Evernote system a go.