Those are ferrite switch mode transformers the electromagnetic characteristics of which are totally different in operation than the typical clunky iron plate linear transformers. The big one is the primary transformer and the smaller one is for the +5V standby circuit. Also you will not find any datasheets on completed switch mode transformers as they are custom wound by/for manufacturers and will more or less only work in the PSU that they were designed for. Reason being the ferrite material from which the core is made out of has been specially selected for things such as switching frequency and saturation along with the pinouts for the windings have to fit the traces on the PSU PCB.
That is not to say you can't yank them off the board and disassemble them to see how they are made and or tinker with them. The trick is the cores come in two halves, and they are epoxied together. Only practical way to get them apart intact is to put them in the oven at around 400-500 degrees and then using some heavy rags (socks work good too) to gently pry the cores apart as quickly as you can while scorching hot. And then you have to be VERY careful not to break the plastic bobbin, not just during the core removal but while unwinding them as well. Oh and the tape is some nasty sticky stuff kapton or some weird high temperature darn near flameproof polymer. You just about have to unwind a little bit, stick it back in the oven to soften the tape up, unwind some more and rinse and repeat until you get it all off.