Come on Arny, you can be more helpful than that!
Soundbars usually include LCR channels. Do you have a "soundbar" or a "center channel" requiring the L/R speakers you show in the corners.
In general, speakers don't like boundaries. "On-wall" can be accomodated, the issue is sidewalls when you put speakers in the corner. Pull the L/R out of the corner, closer to the TV. Don't worry so much about surrounds spacing to walls, but realize they belong to the side, not behind the listener in 5.1.
The same is true of ears. You will hear better sound if you put some space behind your head, and will find the best sound toward the room center.
The one exception is bass, where corner subwoofer placement greatly increases SPL capability, at the price of exciting all the room modes. As long as this is not in the basement (concrete/cinder block walls), you may not have bad mode issues.
Speakers normally want to be at ear level, so you hear the on-axis response. CC's can be above or below; do what sounds good and works for you.
16 AWG is fine.