Cascading two 2-Poles is not a stereo option, but a way for a stronger filtering FX by getting 2 two pole filters in serial. Resulting in a 4 pole filter. But the setting on the units have to be a like and the LFO won't be sycronized.
You might use two 2-Poles in parallel for full stereo. But the LFOs won't by synchronized. And you need to set all the parameters alike. If this is your aim, better try to find the rar Waldorf X-Pole second hand. It was made to do the same job, including saving of settings for stereo signals.
The audio input of the 2-Pole is a monophonic one. So if you would like to feed in a stereo signal, you should not use a special cable to connect both stereo output of the source to one monophonic jack. This is not the proper way. But it does work most of the times.
Better feed your stereo source into your mixer and use one Aux Send channel to send a mono signal to the 2-Pole. And then from the 2-Pole back into the Aux In of your mixer.