Me again.
LW+Octane is very sluggish when node editor previews are activated, small images on top of the nodes. If I disable them then it is fast again. Previews are useful so we can know which image is inside the node. This shouldn't slow down anything. If there is something else connected with previews it should be disabled because it slows things down and is not very useful since Octane is fast enough to preview things in the IPR window.