Tapadh leibh!
So, the question was shortened and the verb (an) was dropped, but the answer implied this verb, so it was "Chan e". And the answer in affirmative in this case would be "'S e", a bheil sin ceart?
Concerning "'S fhearr leam..." agus "Dè an seòrsa as fheàrr leis?": leugh mi Aonad 12-15 agus tha mi a' tuigsinn seo: in the past tense "as" and "nas" (for superlative and comparative forms) becomes "a bu", "na bu". So I see that the verb "is" really implied in these phrases with "'s fheàrr" and "as fheàrr".
Yes, akerbeltz, I know these looking-the-same-and-meaning-the-different words in Gaelic! I think, it is not difficult to discern them when you know the grammar a little better than I do
Mòran taing agus gabhaibh mo leisgeul -- I am asking many questions, because I do like in any case to understand grammatical structure, and in TYG it is not always very easy...