Free Tier 2020.1.3_21.9
1. DISPLACEMENT IS NOT RENDERED IN LAYERED MATERIALS. Layered Materials are rendered without displacement. Displacement works ok on other types of materials though. It used to work well in my previous Blender Octane (may 2020)
2. REFRESH ISSUE WITH ANY MATERIAL THAT HAS A DISPLACEMENT. If I move a mesh that has a displacement or if I move a light, the mesh with displacement is not rendered at all (it disappears from viewport) ... or it takes like 20 seconds to appear. I have to stop and restart render after any change in the scene. There was no this problem in Octane Blender may 2020 edition.
Maybe you have already solved these issues in 21.10 version, but as it's not availabale for free tier, I cannot test, so letting you know.
Nvidia 1080 Max-Q
Free Tier 2020.1.3_21.9, I also have Octane 4, but I guess it's not the isssue