In his first two significant operas, Salome (1905) and Elektra (1909), Richard Strauss continued the post-Wagnerian tradition and composed very heavy roles for very heavy voices. From Der Rosenkavalier (1911) on he struck out in the direction of lighter voices. This is the first noticeable lightening trend since Donizetti.
He even goes so far as to compose a role for coloratura soprano: Zerbinetta in Ariadne auf Naxos (1912). Only Dyer's Wife from Die Frau ohne Schatten (1919) is traditionally sung by a dramatic soprano. My knowledge of Strauss operas is not encyclopedic, so this is based on what I know. I notice that Deborah Voigt, a dramatic soprano, has sung Die ägyptische Helena (1928).
The orchestra beneath these voices continues to be heavy in the post-Romantic style. The idealized Strauss sound is a lyric soprano floating above a posh post-Romantic orchestra. Strauss does not share Wagner's preference for the heavy, muddy center in his orchestration, possibly a wise attitude in support of his love for the soprano voice.
I once postulated the concept of a Strauss legato, a kind of super legato where the singer manages, despite the fact that the text is in German, to invisibly connect the notes as though there were no consonants at all. This may have been based on the style and technique of the great Jessye Norman. The current trend, especially with regard to Rosenkavalier, is to sing the entire opera as though it were recitative.
There is no musical break with Wagner, but he along with Hugo von Hofmannsthal show a significant love for comedy.