It's not you at all - High Sierra appears to completely eliminate the UI lag that some users have complained about on select retina model MBPs. My understanding of Metal 2 is pretty limited to a non-technical level, but I assume this is partly because of how the GPU is now performing certain tasks that have historically been performed by the CPU, because the GPU can perform these tasks more efficiently.
Even in a VM, I have observed what seems to be a much more responsive UI than my Sierra, El Cap, and Yosemite VMs.
I'm very curious to see whether High Sierra reduces normal working temperatures.