The post you responded to in your quoted message claimed limiting the FPS resolved the problem for him. Have you tried that?
Default all apps are capped at 141 for me. Tried uncapped/141/80/60 through Rivatuner, Nvidia and Renpy exclusively - no difference.
No increased disk IO
CPU utilization drops from 16% to 4-8%(No change in memory IO)
GPU utilization increasing to 10-15%(No change in memory load)
Vsync makes it worse
Initially FPS drops from 141(capped) to 60-80, slowly approaching 1fps - this resets when not moving the mouse.
DirectX render is currently unplayable, less than 1 fps.
Main menu splash screen is affected, however submenues like options are not.
Changing window size results in black screen with "0.38.00 Patreon" visible, and blue/red dotted mouse pointer. Negated by opening Shift+G, enabling NPOT, resizing, disabling NPOT and returning to game.
OpenGL render + core affinity set to 5 cores makes it barely noticeable(Still lags when mousing over items), doesn't work for DirectX render.
To make it even more fun, any app hook like RTSS/Ultramon or similar makes it worse. Only seen this issue with RenPy and SuperPowered v0.36+.