When the Mac moved to Apple Silicon the Homebrew devs updated the package install path to /opt/homebrew/bin from the old /usr/local/opt
Of course, while most people will accept the defaults when they install Homebrew you can't guarantee that! You can find brew's path prefix with echo $(brew --prefix)/bin
AppleScript -- indeed, most of macOS by default -- uses case-insensitive matching. If you want case-sensitive in your AS just put your test inside a considering case block:
"Hello World" contains "hello"
--> true
considering case
"Hello World" contains "hello"
end considering
--> false
Completely up to you and your workflow! But it's a common UX design to have dialogs/options be set to "last chosen", especially in batch operations -- of course, some people see that as an annoyance rather than a feature and would rather start from scratch 