Additionally, when I see plugins like sideFX Labs or the Quixel otls, they live somewhere else, the otls are stored in a different folder, yet they are accessible without tweaking the Houdini.env file. How do I get my project setup in a similar way ?
You still have to modify your houdini setup to find the package file though, such as adding it to your home houdini folder, or adding another folder to you houdini path and putting the packages there.