Sorry for the late reply. I have investigated a bit further our topics.
- Use of OCIO nodes (e.g. VRayTexOCIO) for color space conversions is not recommended for performance reasons.
- There is a couple of posts on the topic : https://forums.chaosgroup.com/forum/v-ray-for-maya-forums/v-ray-for-maya-general/72630-render-colour-primaries
- You should use an ODT matching your monitor setup. Forget about the Rec.709 softer look (it is actually confusing, sorry about that.)
- I suppose you load the OCIO config in Maya, for your lights which color picking role are you using ? I know Chaos group has done a pretty good job on Skylight and kelvin temperatures in ACEScg.
- V-Ray 5 (which beta has been released recently) has a much better OCIO/ACES integration with proper IDTs apparently.
There is a lot of confusion on the desaturation of the textures. You can check this topic for a pretty much complete explanation : Linear-sRGB not behaving as expected.
This part is particularly interesting : The RRT is not really neutral and has some sweeteners that can be annoying depending on the context, i.e. glow modifier, red module and global desaturation.
I hope this makes sense and I am not confusing you more. Sorry for the delay in replying.
Chris