About TSynWordBreaker, I have not idea. It seems to be used for scanning words on searching. No for word wrap.
About setting attributes, I haven't played with TSynPositionHighlighter, but I can see that it defines tokens on the positions given. So if you want to give attributes to some fragment of text, you have to "rearrange" the line for to make that fragment to be a token (keeping the state of the other tokens of the line), and then assign the attribute.
FAIK there is not documentation about TSynPositionHighlighter.
Like in many cases, you would have to do, what a suffered Lazarus user have to do, diving on the code, and see what you get.