Thanks. That was a very good article. However, I am not deeply skilled at the level of math or programming needed to know if there are differences between different DAG models (i.e. is there a difference and the same limitations between IOTA, Byteball, or Nano, for example). Any thoughts?
There are differences in the implementations.
This article compares IOTA and Raiblocks (now Nano)
https://medium.com/@peterryszkiewicz/iota-vs-raiblocks-413679bb4c3eAlthough they're all DAGs their consensus algorithms are different: Byteball is a "main chain" DAG, IOTA works with POW, and Raiblocks/Nano is a modified version of dPoS.