The splines are not directly based on auto-keying they are generated each time. Forget the auto-keying for the tracer, that is not connected.
If you change the pen’s path, the result of the Collision Deformer (or tracer) will be different. Change it again - and the results will change.
Set up a small scene and play with it. One of the biggest mistakes that I have seen here for over 15 years now is too little play. Starting with a big important scene takes the learning out of the equation because one might be too careful, and it’s slow, so slow. Learning and getting experience with the tools is the basis for everything.
Just a tiny scene of no relevance and start exploring, stress the parts until they break. The time spent will pay off big times later on. In different words, starting with a big slow scene will not give you the feedback to see what a tool does, its dependencies, and results. A small scene will give you fast feedback, and there is no stress to break something. It is, after all, a test scene. PLAY!