How to compare the topic coherence between models of different number of topics?
After doing some more digging -- it appears that gensim's functions output difference calculations 

This below actually does what I am describing above:

cm = CoherenceModel(model=model, texts=docs, dictionary=dictionary, coherence='c_v')


While this below is actually only the summation across the topics of the model not divided by the total number of topics in the model. 

top_topics = model.top_topics(texts=docs,dictionary=dictionary,coherence='c_v')