A lot of Netflix currently is DD 5.1+. But your AVR will upconvert any DD 5.1 track to Dolby Surround, which will give you convincing overhead height effects even if it's not a native Atmos soundtrack.
Personally I would take 5.1.4 over 7.1.2 because I find 4 overhead channels more immersive than 2 overhead channels with surround backs. But opinions vary of course.
You could always go 7.1.4 with an external amp for the 2 front channels - as the 6013 does support 11-channel processing.
The Prime Elevation will work well for side surround, rear surround and overhead height effects and has a built-in wall mount bracket. Be sure to use the ceiling safety lock if you mount Prime Elevation on the ceiling.
Prime Satellite also works well for these channels - but you would need to source a wall/ceiling bracket. Prime Satellite has a 1/4-20 threaded insert on the back for ball/clamp style brackets.
My own HT has four Prime Satellites on the ceiling with a ball/clamp bracket and the L-shaped rod. They hang naturally at almost the perfect angle and just needed to be toed-in. But they are more visually conspicuous than Prime Elevations.
In addition to the link shadyJ provided above - you can also go
here and see all of the Dolby Atmos system variations - and they will also provide recommended speaker placement. The most common ones we recommend are overhead down-firing:
While they don't specifically mention the recommended height for the side surrounds and rear surrounds, we've found that about 1 foot above ear level when seated works well. You don't want to mount the side/rear surrounds too high, of you'll lose the horizontal plane of envelopment.
