Transformerless (aka "capacitive dropper") power supplies are never used to supply more than a few watts of power, and even then they rarely cost less (or take up less volume) than a competently designed flyback.
Telecom power supplies are designed for very high reliability and efficiency, with upfront cost almost not even a consideration. The most common topology I've seen is a boost PFC front end either feeding a phase-shifted full bridge (for >500W) or an LLC half-bridge (<600W, yes, some overlap there). Cooling depends on the power level, obviously, but typically forced convection is used starting at relatively low power levels (say, 300W) because telecom supplies are often crammed together in a 19" rack so don't have a lot of means of shedding heat via radiation or natural convection.