Why Some SMPS use Tiny Switch, Some use Top Switch and Some use Link Switch and Other use PWM IC. Please guide what is the criteria to select?
It's all about power delivery to the load: -



Taken from this data sheet

PWM control ICs require an external MOSFET (it's built into power integrations switch products listed above) and because it has an external MOSFET you can tailor the design for more specific applications or even higher powers.