What is the best folder to install your extract-only applications?
In general self-installed UI applications should go to /Applications, unix-level binaries/applications to /usr/local (see Where should shell tools be installed? and I downloaded a shell executable and man pages from a source I trust. Where should I put them?). But can spare yourself a lot of hassle by using a package manager for this, mainly Homebrew or MacPorts (using both at once is possible but requires additional configuration steps).
Homebrew
Helm seems to available on Homebrew already, so

Install Homebrew as described on the site
Install Helm with brew install helm
To get older versions of Helm follow the instructions in this discussion

This will install Helm (and any other installation you do via Homebrew) beneath /usr/local (for Intel) or /opt/homebrew (for Apple Silicon). /usr/local/bin most probably is already in your path, /opt/homebrew/bin needs to be added manually.
Macports
Macports has several versions of helm available port search helm and a helm select port to switch between them.

Install Macports
Get the dmg Disk Image for your version of MacOS and run the installer from that.

Part of the installer can update your path in your shell startup files i.e. adding /opt/local/bin to your $PATH
To build things you will also need Xcode (now from the App Store) and install command line tools xcode-select --install and for current OS Agree to Xcode license in Terminal: sudo xcodebuild -license . However macports does download binaries in most cases so how much of this is needed could differ.

install port
e.g. For Helm 3.3 sudo port install helm-3.3

Add the select port sudo port install helm-select This will allow you to choose which version of helm that will appear on your path.