CG render sanity check - MtoA Nuke

Alright.
Done some more fiddling in Maya/Arnold.
So if I understand it correctly, when I’m picking a color in the color picker and have ‘Color management’ ticked off, I’m setting the color in the sRGB range, right?
Because when I set R to 1, with ‘Color Management’ ticked on, and then turn it off, the R value goes to 1.308.

Also, are there any rules to the Cornell box or am I overthinking this?
I don’t know why, but I thought the red wall had to be (1,0,0) and green (0,1,0) in sRGB.
But that all looks so bright, so I started wondering if it just had to be a red and a green value.
And then match it in comp.