Heyas! I did this whole course with a 1070 (updated drivers) in 4.1 and it was pretty smooth. I did use a Blender Studio addon called EasyWeights which, with the shortcut set up on my Quick Favorites menu, allowed me to toggle back and forth from weight paint mode easier/faster than the regular method. Perhaps this might help?
The addon is available from Blender Studio in a zip with a bunch of others. I just unzipped the file and installed the appropriate .py file. For 4.2 it appears to be available via Extensions in Preferences.
