Have a lot of lag and bugging problems in Harmony when working on my Macmini that I never had in Animate 3. Any suggestions to cut this out minus getting a more powerful computer?
Your graphics card is the weakest element in your system. Keep Full Screen Antialiasing off in Preferences.
Keep your projects small. If you have a story outlined find places to break it up and work on smaller than usual sequences. Then piece them together using video editing software.
Keep scenes on the simple side if possible and avoid heavy overhead from multiple effects.
I am wondering whether the textured brushes require more of the hardware then the most simple brush options. You could try testing various brushes and pencils to see whether some are more responsive than others.