CrowleyHead points to Young Thug emerging from Atlanta Future Swag music. He says that its infantilism is an important pre-cursor to the style Thug went on to develop and crystallise.
You can hear this in his early mixtapes.
Thug gained a greater degree of prominence with the release of 1017 Thug and Rich Gang: The Tour Pt. 1. On these projects Thug forefronts the verbal absurdism (phonetic dada and unconventional use of pitch) that artists like Future had only touched upon.
In the middle of the decade, ambient-tinged, cloud rap-inspired instrumentals began to really take over rap, arguably providing dreamy soundscapes more complimentary to Thug’s style than the midi-horn fanfare that had dominated previously.
Later in the decade Migos crystallised a new rhythmic lexicon in rap that relied heavily upon staccato fragmentation and interjection, which informed Thug’s style.