Apple Silicon isn't yet at the RTX GPUs level but getting there.
There is the hardware acceleration option in the preferences (Devices tab), besides that it's just scene optimization.

And default to grayscale/floating node instead of RGB, since it's used in a greyscale manner nearly exclusively.

And default to grayscale/floating node instead of RGB, since it's used in a greyscale manner nearly exclusively.

Same monitor?
Same connection cable?
Same Nvidia control panel settings?
Same Windows Color Management?

Are the Blender Color Management properly set (to "Raw")?

Some more information regarding ACES and Octane Blender Color MGMT.

General Octane Color Management
ACES in Octane
OctaneRender Blender Color Management

For cheating the shadeless option : I use a diffuse material with roughness at 1 an use the emission input socket.
In the texture emission node I put the power to 1.

Could you elaborate on that? There is the solo-diffuse-material trick but not sure I interpret this "shadeless cheat".

Could you show the mismatch you are getting?

There isn't nothing to tweak as long as it follows the Universal ACES workflow. The only particularity is that Octane is a Spectral Renderer but it shouldn't make a huge noticeable difference in such a case.

stuz0r wrote: All in all, it's not a big deal. I just liked the look of the older version a little more.

Can't sleep at night. Now we need to know.

I'd suggest sending it here, just in case it doesn't receive the attention it deserves.

As shown in the Cycles version, there's room for improvement :) And when you triangulate STP objects, in most cases cleaning up the mesh and physically beveling them is out of the question. Nobody has the time (and down the line money) for that.
I replied a second time prior to seeing your reply ...