it's all heresy since a "limiter" is an all encomassing term for a compressor with a very high compression ratio.
how it does it's compression is a different topic, and the first term (soft clipper) is one example of how compression can be added, although it's not common in pro audio compressors.
for an example, there's a clipper type limiter circuit in
my behringer mdx2200 composer pro. it's separate from the main compressor circuit (and of course there's one of each for each channel). the "limiter" has it's own knob. it sounds like ass. you can hear the distortion from the clipped waveform. if this was a soft clipper I guess it would be less obvious. if it IS a soft clipper then it's not very soft... either way it's junk.
fortunately the compression circuit itself actually is a far better limiter if you crank it's compression ratio and set it's other parameters as you would a true limiter. however the box isn't terribly well suited to limiting in general due to artifacts at that much compression (as is common with most inexpensive compressors).
so how the compressor does it is by lowering the level extremely when compression is set to limiting levels (20db or greater sort of as a guideline). the extra (crap) limiter does it by chopping off the top and bottom of the waveform above a certain level. nasty stuff. most true good quality audio limiters don't do it the way the berry's extra "limiter" does it, most just do it the way the berry's compressor does it which is far superior.
my best limiter is an 1176. it can do 1:20 compression with nearly instantaneous attack times. amazing stuff. and it doesn't sound like crap at that level. but it's a far more elaborate circuit than the vca compressor in the behringer (or most other compressors in general in fact). and the 1176 doesn't chop off the tops of waveforms when it's "limiting".
cheers,
Don