LMP91000: Filters calc

Part Number:LMP91000

Hello, I'm designing a board with the LMP9100 for Alphasense 4-electrodes sensor based in once design that you uploaded on other post. I would like to be sure that the design is correct before send the board to prototype, and I don't understand very well the filter configuration. In this design:
www.ti.com/.../snoa922.pdf

You implemented two filter, once a RC in Vout, and other in the Amp:
1. In the first once, why you didn't place the resistor? (page 26)
2. Why two filters?
3. What cutoff frecuency do you recommend?
4. In other case... How I must calculate the cutoff frecuency?

Thanks you!