First, thankyou for your hard work creating this, integrating with Unity, and offering a free version. https://imgur.com/a/oG7Ut
In the above link are two different Unity3D scenes. One is an unedited demo scene of the OTOY spaceship, I might have moved the camera just a little bit. The other is a project I'm working on. The PBR Viewport in Unity is much too dark and significantly does not represent the final render. The good news is, the Octane Render screen looks like the exported image from the PBR Viewport, but that really doesn't help me when I'm trying to work directly in Unity.
* Unity 2017.3.0f3
* Octane Plugin Version: 18.104.22.1683
* Octane version: 3.07 (3070007)
Hardware is Asus GeForce GTX 1060 6GB
Let me know if there are any settings you need.