If one spends enough time to carefully explore the area, there are many temples here that have been overgrown by strangling fig trees in ways that do not fail to charm any visitor. I visited Sambor Prei Kuk as a halfway stopover from Phnom Penh to Siem Reap via a rental car. The three clusters have all been well reviewed already, so what I can add here is about the Trapeang Ropeak temple complex west of Prasat Yeay Poen. Its temple Z is originally surrounded by four shrines forming a quincunx, of which only one of these ruined octagonal shrines stands (there are only 11 of these unique octagonal structures remaining, so its good for ticking off as much). The carvings on the temple are in relatively discernible state, and the vault is described to be irregular but is complete compared to most that have collapsed. A stone throw away is another octagonal temple named temple Y, and it is spectacularly taken over by a tree. In the afternoon light, these two temples are photogenic as there are no tree covers above them. I recommend making the swing here after seeing Group S as a way of capping off a visit. 

PS. Prasat Tao (Group C) is currently off limits due to conservation work, and no one can get near the famed lion statues. The same is the case for the main temple in Group S.