Both madd lazim kalimi mukhaffaf and madd lazim kalimi muthaqqal arise from original sukun after a madd letter inside a word. The difference is whether the following articulation becomes doubled. This is a feature of the word, not of a fast or slow reading tempo.
«آلْآنَ» — mukhaffaf: the relevant original still consonant is not doubled.
«الضَّالِّينَ» — muthaqqal: the lam after madd is doubled.
By contrast, «جَاءَ» is classified by the following hamzah, not an original still consonant. Thus to distinguish muttasil, kalimi mukhaffaf and kalimi muthaqqal, identify the cause and observe whether shaddah is present. Preserve the actual consonants, not merely the rule names.