I guess you have to be clear what you want to get out of the trip, serious NGS like documentary photography, travel photography, history, or been there done that.
Other than many historical artifac, the apsaras, the carvings on the stones - if you got a good guide to explain the story behind the carvings - can be very interesting. Then it will be how you could picture that story.
5 days can be long, or it can be very short as there are only 5 sunrises and 5 sunsets if you really want to get one best shot, you may have to revisit the places and get the time, the angle, the pond reflection well. - hey the monk in robe won't sit still waiting for you, unless you hire one to.
I find there are more lifes within the SR compound, kids touting, - these are good candid shots.
Alternative to road to PP, you can evaluate boat via Tonlesap, while it is typically overloaded and the boat risk overturn - but this is life.
I personally find it hard to take photo at the KF and the prison, it can just be emotional overcoming what to do take, the souls?
I prefer back to life on the street, like SR or PP, where it reflects the future of the Cambodian, the hope. I do hear that it is not so safe, keep the travel simple and low profile.
I have not been to the green though I shoud have, just follow advise. I don't think the mines are fully cleared - never - so follow cleared path and always have a local guide, it may just cost you a couple of US$ to hire one.