There are about 4 million ways to "clip" without showing clips (a brick-wall limiter being one of the most popular, if not one of the least effective).
Straight clipping of the output buss will do some pretty weird things with some converters... You might not hear any of it while you're in floating-point - but once you're 16-fixed, you're going to know something is wrong...
The other part of the question -- A mix that can handle excessive loudness without crapping out is usually the result of high-quality recording. Lots of headroom (the more the merrier in most cases) at every single possible step in every single possible phase of production, proper and reasonable gain-staging through quality gear, etc., etc., etc. Up to and including the mastering process. Without a doubt - The projects that come in here the "quietest" (many of us would call it "normal volume") tend to come out the loudest-slash-best sounding.