If you already have the previous RUNE version installed, you generally do not need to re-download the entire game. You need the Update Patch release: Baldurs.Gate.3.Update.v4.1.1.3630146-RUNE .
Beyond the performance buffs, v4.1.1.3630146 fixes several frustrating edge-case bugs: Baldurs Gate 3 Update v4.1.1.3630146-RUNE
May your rolls be natural 20s and your framerates be stable. Baldur’s Gate 3 — Update v4