[Chloro-Bromides < I ignore these and feel that they are too hard for starters]

In what sense?

[No Cl/Br crystal of a defined ratio of halides can be made by a single run. You must use a double run of Silver Nitrate and Halide both to form a mixed halide Cl/Br with a clearly defined ratio in every crystal.]

Do Cl/I or Br/I or Cl/Br/I differ in this respect?