To answer,

> Do you usually blind type?

Yes.

> If so, what advantage does it bring to you to look down on your keys?

For simple actions (like opening a new tab) there is no need to look down on keys. IMO this is little Apple's fault, whenever I use a tabbable & Touch Bar-usable application I set the new tab button on the right. I usually place the trash button (on Finder, Mail and some other apps) on the middle of the Touch Bar.

For some more complex actions (like selecting an emoji/suggestion, or moving between photos, etc...) it's just as fast/faster to glance over and move your fingers instead of using shortcuts/trackpad.

> Also, in an optimal seating position (elbows at 90 degrees)

I'm not sure if I'm in optimal seating position, but... (If you're meaning if my elbows are on the same height of the display yes)

> do your fingers obscure the visibility of the touch bar?

No, not at all. I can clearly see the Touch Bar whether my fingers are.