Most All switching power supplies are regulated. I think you mean does it have over voltage protection. The Meanwell rt-50b does have over voltage protection. Its over voltage that can kill your Amiga,C64 etc.
Generally poor 5v regulation will just sag on the 5V rail going low,not high in most cases.
Low voltage generally will not do any damage.
For example,4.9volts wont hurt anything,but 5.4volts could start killing parts. I've seen a4000's that will not reliably boot at 4.92v.
Plus or Minus 5% is usually acceptable on 5V rail.
Most modern ATX power supplies regulate poorly on the 5V rail because pc's have moved to using 3.3V and 12V mostly.
Some ATX power supplies need a good load on the 5V rail to regulate properly.
If in doubt check the datasheet for the power supply in question,it will usually tell what protections it has.