did not know FC when he said this either - All he knew was that Emma was disposed to like him and that only a blind man would not find Emma pretty.

I think all CW knows of Elliot at this point is that Elliot admires Anne and Anne seems to enjoy his company.

IMO, both Mr. Knightley and CW take a dislike to their rivals for the same reason without really knowing anything about them - ie jealousy.

But, yes, you are right about what Line meant - Anne distrusts Elliot because he appears to be everything to everyone and Knightly said that the ability to adapt yourself to please everyone was not something he would admire in a person. Both Anne and Knightley prefer people with an open temper which attracts them to CW and Emma, over Elliot and Jane F. So Anne and Knightley do seem to have many similarities in their personality preferences.