For FPPS it will pay the block reward AND the transaction fee theoretically. How each pool calculates the “theoretical” transaction fee will differ. At NovaBlock, we take the average over the past 24 hour period to ensure it is fair.
I stand corrected, there is indeed a difference, but given the fact that transactions fees are the way too tiny in respect to the block reward, getting the transactions fees in PPS or PPLNS makes a little to no difference, especially when mining with large pools that actually find blocks, if however, you mine with a small pool that offers PPS then yes maybe you want to make sure it's FPPS and not PPS+.
Thanks for the clarification.