Spheroplast efficiency can be checked by osmotic sensitivity. Resuspend 100 ul of treated cells in 1 ml of 1M Sorbitol. If you add 100 ul of 20% SDS to the cell suspension, spheroplasts should lyse immediately. So you can measure A600 absorbance for efficiency and compare with the control.
Since spheroplasts are very fragile, we measure their formation effiency by adding 5% SDS, which will induce them to burst and we do cell count or OD600 on treated and no treated samples.