My platformer character is only moving by full pixels

How can I make him move by subpixels? The sprite is 8x8 and the camera around 150x100, so his movement is looking very bad and not smooth at all. I tried unchecking “round coordinates” in the plafformer behavior options of the player but that chaged nothing.

Or do I have to scale up all graphics to get smooth movement? I have been looking for 2 days but still haven’t found a way to tell the engine to draw a sprites at it’s real position.
Does anyone know how scaling everything up would affect performance?