The acrylic did not have any coating of paper on it...it was just the plastic surface that I cut.
I would say the 6.3mm Balsa was 'soft'. Cutting it was quite easy, quick and clean around the edges.
The 4.7mm was what I would call a 'medium' hardness Balsa and I could not cut it using 6 passes. I could use more passes but the cut lines were already getting wide and burnt, so by the time I could have cut through it with, say, 9 passes, it would have have been a pretty cut.
The 2.3mm was a 'medium' hardness too and although it took 5 passes to cut, the cut lines were still looking good on the surface after 5 passes.