Source > Adaptation
VNs (Steins;Gate/Steins;Gate 0, Clannad)
The Disappearance of Nagato Yuki-chan
A Silent Voice
Adaptation > Source
4-komas, typically (Bocchi the Rock, K-on)
Music anime (Your Lie in April, Sound Euphonium, also the aforementioned Bocchi and K-on)
Simple art styles, extrapolated (Senpai is an Otokonoko, 4-komas)
Almost anything KyoAni touches (Violet Evergarden, counterexample in A Silent Voice)
Selective adaptations (Insomniacs After School, Usagi Drop)
Say I Love You (except for episode 12, which I think is anime-original)