My primary OS is OpenSuse 42.3, which equivalent to SLES 12. It has KDE 5.8 and Gnome 3.20. My preferred desktop is always KDE--I used Gnome in the past but found it to be inferior to KDE. When they messed with the last decent version of it, I have disliked Gnome since inception of v3. If am forced to use it--I revert back to Gnome Classic.
I previously used your exact configuration months ago in KDE with no performance issues. I am currently at Browser 3.20 and my databases at 3.5.6 & 3.5.7 with no performance issues. I have not used Gnome recently, I could check to to see if running Neo4j in the Gnome desktop makes a difference.