This was a worse problem a few point releases ago. At that point the screen redraw was achingly slow and the handles on the curves panel wouldn't update when you moved the cursor, so it was almost impossible to actually use the curves panel on large and complicated files on a hidpi screen (it's much happier on my second low-dpi screen; but hates both the hidpi main Windows screen and the hidpi mac laptop screen).
Now the screen redraw's great - really impressively fast. But the handles on the curves panel lag way behind. You have to do the adjustment looking visually and then hold the cursor very still and wait until the handle on the panel updates. Very weird - wouldn't have thought the handle would be the tricky bit to get smoothly udpating!