I have Plasma (as Neon User) 5.14.3, fully updated as of the moment installed on my laptop which uses the Intel HD 505 integrated GPU. Kernel is 4.15.0-42 (Ubuntu).

I've noticed that my framerate on any of the benchmarks I tried was half of what it had been with other DEs on the same laptop and with the same Ubuntu 18.04 base. I had previously scored, for example, in the 550 range on GLMark2 (2014.03+git20150611.fa71af2d, from Ubuntu repo) on Cinnamon Mint 19, with the modesetting driver performing slightly better than the Intel one.

I did a bunch of trial and error, and I've discovered that in Neon, the combination of the modesetting driver, the OpenGL compositing backend (either 2.0 or 3.1), and the Plastik window decoration theme cuts the reported performance/framerate in half (score on GLMark2 down into the high 200s; other benchmarks show similar percent losses). If I eliminate any one of these things by selecting the Intel driver, Xrender backend, or Breeze window decoration, the framerate goes back up, though I note that there is a slight performance penalty with Plastik using the Intel driver (~5-10% score) compared to Oxygen. I had previously thought there was no difference between window decorations with the Intel driver, but there is a small difference that is repeatable.

The Breeze and Oxygen window decorators restore the same performance that I got with Mint, using either driver. I haven't found any other decorator or theme that will not slow it down greatly with the modesetting driver. All of the Aurorae themes come in at about halfway between Plastik and full performance (score about 400 on GLMark2).

There is no slowdown at all in my desktop PC with Nvidia (proprietary driver) and the same kernel/Plasma/Neon versions.

I like Plastik more than any of the other decorators/ themes, and while the 5-10% loss while using the Intel driver is tolerable, the Linux world seems to be gravitating toward the modesetting driver for Intel iGPUs, and I've seen some minor bugs with the Intel driver that I have not seen in modesetting. Any ideas if it is possible to restore the lost performance while using the Ubuntu and Neon preferred modesetting driver and Plastik?