I'm using SP720 for analog circuit protection in a number of instruments since about 10 years. I must confess, that I didn't yet measure the devices crosstalk capacitance (input pin to input capacitance), but I won't expect a value above 0.1 pF or so. In other words, the external circuit crosstalk capacitance will be most likely larger.If you are dealing with high impedance input signals, it may be unsuitable to bring the signals close together at all. In this case, you won't want them to share a common IC, whatever it is.
SP720 is particularly good for low capacitance protection of high speed signals. For a drum sensor, regular silicon diodes seem sufficient in my view. Or just a series resistor, utilizing the internal substrate diodes of the connected ADC or amplifier chip.