about lightroom cc 2015.8 or 6.8 have you noticed a better perfomances according
Lightroom CC (2015.8) / 6.8 includes ‘under-the-hood’ changes designed to improve the responsiveness of your Lightroom experience. You should notice improements in image editing responsiveness when background tasks (such as Preview Generation) are running, moving files between folders, running catalog backups.
under windows 10 pro 64bit?
You also need good system specs for the better performance, you can refer the minimum system requirements here: System requirements for Photoshop Lightroom for Mac and Windows OS