This paper focuses on the post-lexical tonal properties in Thadou and Mizo, the two Kuki Chin languages spoken in North-East India, and tries to typologize them based on the interaction of phonetic and phonological modules in the grammar of these languages. The paper investigates the different downtrending phenomenon like the declination, downdrift and downstep and accounts how the pitch is realized differently in each of these languages. The study reveals that the gradient implementation of certain phenomena in the phonetic component may be severely constrained by the nature of the lexical and post-lexical phonological component in a language. The results of this investigation thus reveal two varied types of post-lexical tones among the Kuki-Chin group of languages.