Alright I did some testing and both GDI and OpenGL renderers are working with high fps now (144fps which is my monitors limit), and the cursor is buttery smooth!
But in order to get GDI to work I had to disable freesync. If freesync is on it feels like the game limits itself to around 60fps (fraps and msi afterburner fps monitors don't seem to work with GDI), but with OpenGL high fps works with freesync on.