Here’s what those settings specifically should (most likely) look like for you when everything is set up using the instructions above:
I can explain the rationale behind each of these if you’d like, but these three transforms are actually the defaults when loading the actual ACES config… How convenient!
The important setting to note here (other than the view transform) is the “Apply Output Transform to Render” box which should be checked off. This is because we’ve set our rendering space to ACEScg and in our render settings we’ve told Arnold to dump that raw output right into the EXR and not apply any transformations so that we have all that data to work with over in Natron. If you’re only using ACES for your 3D rendering space and conforming to some other gamut for comp (don’t really know why you’d do this) this is the setting you’d change to make that happen.
The apply transform to playblast box is checked on so those will be rendered with the sRGB transform from the viewer, this way playblasts will look correct when they’re rendered to video files.