I recently updated my MBP to run 10.14.6 and Parallels 15.0.0. In summary the performance of my Mac and VM's (using the Parallels Hypervisor) is pretty much back to where it was before I started to have issues.
When I started the VM's after the upgrades there was a very long delay, maybe 5 minutes, before the VM's actually started. I thought the system was hung but they eventually started (Windows 7 and Ubuntu) I assume the VM disk image was being read or something. The 10.14.6 release notes did mention a performance fix relating to large files and my VM images are 100GB+.
So for now, I'm happy with Parallels again but its a reminder just how critical Parallels is to my business. Its also nice not to have the fans spinning all the time on the MBP.