What kind of file are PlayerPrefs, how can i pass them on to another project and / or export them to a unity package?
for example, if i want to keep procedural trees as PlayerPref arrays, and not mesh, how do i keep the arrays as files in a unitypackage?
Player prefs are stored outside of project directory and hence will not suit your requirements. You rather stream your data to a file (example here http://unity3d.com/learn/tutorials/modules/beginner/live-training-archive/persistence-data-saving-loading (in the second part))