Board Thread:Theories and Speculation/@comment-45444155-20200728155230/@comment-26636534-20200729132502

Sage transformation is a physical condition of Jugo's clan to passively absorb natural energy all the time, due to a special enzyme their bodies produce. It's essentially a kekkai genkai.

Sage mode is being able to actively gather natural energy and balance it with your normal chakra to produce sage chakra.