Hi,
If you were making an 500W SMPS for a class D audio amp.....175Vout.....then it will be slow in feedback loop because of the opto feedback...so wouldnt it be a good idea to have the offline SMPS produce say 100Vout...then have a couple of non-isolated, interleaved dual boost converters swithcing that to give the 175V, 500W?
Slow feedback is relative...and this usually isn't a problem, generally.
Maybe you expect voltage fluctuation?
But the voltage fluctuation also depends on several things, like: output current (waveform, frequency, magnitude), bulk capacitor size, additional filters.