You can do it however you want,dont listen to the must light the whole room BS.Thats just the opinion of someone trying to sell more lights.If you want to fill the room with plants in pots light the room,if you want to do tables or beds just light the rows.
I run gavitas not nanos so cant really speak to optimal distance from walls for that fixture but if they throw a similar pattern its about 4'x5'.If i was going to do that size room with 8 lights id probably go with 2-4'x20' rows/tables/beds with 4 lights turned sideways over each.To light the whole room your probably looking at more like 12-14 lights or so,good luck!

I did quit abit of research before I hung my room. They are supposed to be designed for a 5x5 spread at 3 feet from the canopy. I run em 5 feet apart to give 2.5' on each side. B.A.F.... So If your plants are going to be right next to the wall I would put em 2.5' off the wall. I'm running 2 rows of eight in a 12 x 50' room, seems to work well. If you put the center of the hood 3 feet off the wall on each side that should fill the room nicely. You'll have 5 foot spread in the center of the room and to the wall on the sides. They are bright so I wouldn't worry about being too exact. Good luck

I'm running 3'x6' beds,

"turn lights sideways" your saying mount them perpendicular to the beds/tables so the light thrown out the side of the lamps overlaps itself?

Designed with a 134 beam angle ---to be about 5 foot centers.

Walls are good. They are effectively an extension of the reflector. it's better to have a wall reflect light back into a canopy than to have the light dissipate into nothingness.

shhhh.. shhhh.. the interlacing overlap is the secret.