(?:

 # -- Words/Characters
 (                       # (1 start)
      (?>                     # Atomic Group - Match words with valid breaks
           .{1,16}                 #  1-N characters
                                   #  Followed by one of 4 prioritized, non-linebreak whitespace
           (?:                     #  break types:
                (?<= [^\S\r\n] )        # 1. - Behind a non-linebreak whitespace
                [^\S\r\n]?              #      ( optionally accept an extra non-linebreak whitespace )
             |  (?= \r? \n )            # 2. - Ahead a linebreak
             |  $                       # 3. - EOS
             |  [^\S\r\n]               # 4. - Accept an extra non-linebreak whitespace
           )
      )                       # End atomic group
   |
      .{1,16}                 # No valid word breaks, just break on the N'th character
 )                       # (1 end)
 (?: \r? \n )?           # Optional linebreak after Words/Characters

|

 # -- Or, Linebreak
 (?: \r? \n | $ )        # Stand alone linebreak or at EOS

)