About the "Unable to watch for file changes in this large workspace" warning, this is a bug, which is reported here:
So please don't worry about those instructions. It's fine to just ignore this warning because it doesn't mean anything.
About the "An unexpected error occurred when locating the Git executable" error message, there is a bug report for it here:
You can also safely ignore this. Arduino IDE 2.x has some advanced optional capabilities to integrate with Git repositories, and that can only be used if you have Git installed, but it is not needed for any of the normal usage of the IDE. If you don't have Git installed then you wouldn't have any interest in the Git integration anyway, so you won't be affected at all by this and can safely ignore it.
I know it is not a good experience to have these confusing messages on startup. Arduino IDE 2.x is still in the beta development phase and undergoing continuous improvement. I'm hoping these will be resolved in an upcoming release.