what you call "oblique 90" I usually call "top-down"
Top down means something completely different than what you imagine:
top-down:
viewing angle 90°third vanishing point can't be seen because it's like a map seen from above.
Super Swiv

Hotline Miami:

"RPG"-view
viewing angle 45°
third vanishing point is infinite, means straight z-axis

and inbetween are the
"Zelda" projection (more topdown, 3rd vanishing point implied - strognly breaks a projection, most symbolic approach of all these here)

and Golden sun: (more RPG view, third vanishing point implied, only breaks the perpective/projection slightly (houses), but their cliffs are still drawn with an infinite third vanishing point.)
