Silvershower Heartstrings is the closest fit on the game's own numbers: Yelan's kit multiplies HP, and a weapon is ranked here on whether its ascension stat and its passive act on that stat. The Daybreak Chronicles, Sequence of Solitude and Astral Vulture's Crimson Plumage come next. No playtested ranking has been imported for Yelan, so this is arithmetic over the kit data rather than a damage measurement.
Run Heart of Depth on Yelan, with Nymph's Dream and Tenacity of the Millelith behind it. Main stats are HP% sands, Hydro DMG Bonus goblet, CRIT Rate / CRIT DMG circlet. Roll substats in the order CRIT Rate > CRIT DMG > HP% > Energy Recharge.
Talent priority is Normal Attack > Elemental Skill > Elemental Burst. The Elemental Burst costs 70 energy, which is what an Energy Recharge target has to clear.
The strongest team is Yelan, Furina, Kaedehara Kazuha and Sigewinne, built around Yelan: Anemo · Mono Hydro.