What kind of filtering does this op-amp perform?
The signal conditioner ought to match the bandwidth spectrum of the signal. You can use Falstad's simultor to sketch the circuit with an OpAmp and trace the result with a log swept sine input.  Due to limitations in this AC analyzer for low freq=1Hz, I scaled all frequencies up 3 decades by reducing  all C's down the same.

As expected it matches the spectrum of a heartbeat at 120BPM or 2 Hz.  In theory , if my assumption is  true, this is called a "matched filter" the optimum for signal conditioning to max SNR.



With lots of practice, this took me 10 minutes, and another 10 to edit the screen shot and make it pretty.

Here's a built-in filter