Many users reported better performance in act 3, specifically within the crowded city of Baldur's Gate, which was notoriously performance-intensive.
Baldur's Gate 3 updates often require significant temporary space. For example, Patch 7 required roughly 160GB of free space for the installation process, even though the download was much smaller. Save Games: Baldurs Gate 3 Update v4 1 1 6072089-RUNE
Run the RUNE installer ( Setup.exe or Patch.exe ) and manually point the installation target path to your main Baldur's Gate 3 root folder. Many users reported better performance in act 3,
What or behavior are you experiencing?