Summary - most of these issues are unique to latest macOS systems and are not problems for Windows machines. The Slicer development for macOS has lagged behind a little bit because there are just fewer developers using macOS to help support these platform specific issues. Reviewing the download statistics in the past year, macOS accounts for roughly 23% of downloads compared to 68% for Windows. Unfortunately there is no firm timeline on when macOS on latest Apple hardware will be optimized in an easily downloadable Slicer installer from the Slicer website.
Regarding 1) Yes this is generally a known issue when running the Slicer Preview because it is not signed and notarized each night. Have you tried using the Slicer 5.10.0 stable instead?
Regarding 2) How much memory does your MacBook Air have and how large is the CT scan that you are loading and analyzing?
Regarding 3) There is an issue with a TotalSegmentator dependency requiring a newer torch version however Slicer on macOS is running an intel built version rather than a native Apple silicon ARM64 based version. The Torch dependency however hasn’t been providing latest versions for Intel built apps running on macOS. Slicer is running an intel version on your system through the Rosetta layer which you might have had to install when you got your new computer.