Same problem here. I have a Threadripper 1950x, 64GB of RAM, a Soundblaster ZXR and a GTX1080ti, and I experience truly bad performance from even the latest version of SO4. By contrast, I experience absolutely flawless performance and playback from FL Studio 20, Mixcraft 8, and Reaper. I have no idea why this happens, but I have reached out to tech support on the off chance they can spot something.