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