Can you mix PoE and non-PoE devices on the same switch ?
Yes, PoE does not interfere with normal switch operation. PoE and non-PoE devices can be mixed on the same switch.
In addition, many PoE switches can automatically disable the PoE part of the signal for ports that do not need/request/support it, making them more power-efficient.
PoE is a DC signal/current that does not interfere with data signal, even if sent through the same data pair. In 10/100 networks, the two unused cable pairs are utilized for PoE. In Gigabit networks where all four pairs of cables are used, phantom power can share the same wires as data without issues because of the different frequencies.