Hi Yaron, I assume that when you say "commitments" refer to budget control and commit.
In that case if you want to integrate SRM with FM you must active PPS but if you just want to control and commit budget via CO it is possible without PPS activation.
Take care about to active PPS as there are lots of inconveniences with other functionalities.
Regarding scenario if you choose to active PPS it is mandatory to implement extended classic otherwise if you choose not to implement PPS it will be possible to implement both classic or extended classic.
Hope this help !