Color primaries shifting and Negative values (OCIO) confusion

Hi @nick, thank you so much for the clarification. It’s not far from what I thought was happening, but it was based on speculation, and it’s great to get clear answers.
So I guess I’m used to use Linear AWG for comp in Nuke.
How would one handle the negative values resulting from working with Alexa plates in ACEScg? It’s visually weird as these areas are bright highlights that become very dark, and keyers don’t like it at all.

Also as a side question, are AP1 and RGB primaries similar? On the CG side for linear workflow we usually work with linearized sRGB textures, that then get rendered “as is” both for the old linear workflow and the new ACEScg workflow. If the primaries are similar I think we’re good, but if they are similar that means we’re missing one step of putting our textures into ACEScg first?