I would describe my ability to visualize as almost exactly like that in the article. I can't answer these questions directly, but I can tell you that when I am falling asleep there is a 'switch' that turns on in my brain and all of a sudden whatever I'm thinking about will appear before me in full detail, color, texture as if I were viewing an image of it. The sudden change has been enough to wake me up at times, otherwise I probably just forget about it as I drift asleep.

Similarly for sounds, except that I can always imagine sounds. However I can only imagine sounds that I can try to 'subvocalize' with my own voice (plus humming, whistling, etc.). When on the verge of sleep I will hear gorgeous, fully orchestrated (as far as I can tell) songs. Sometimes memories of ones I know well, sometimes either something I don't recognize or am subconciously improvising. It's extremely alluring and makes me annoyed that I can't do this at command. (Though friends who always have a tune of music in their heads tells me it gets annoying too.)

Number 8 makes me think the author is even more extreme than I in aphantasia.