OK, I'm embarrassed to say how many YT videos I've watched today. Let me see if this make sense to the experts!
Basically I have 2 options:
1) Add the Legacy Powermaster which basically then transfers the power of the ZW handle to the Legacy handset.
2.) Add ERR Cruise to the engines to get effects similar to TMCC/Legacy.
Let me start by saying, most of my knowledge has come in the form of those very same YT videos so don't be embarrassed, you are that much closer to being an expert.
1) Add the Legacy Powermaster which basically then transfers the power of the ZW handle to the Legacy handset. You have this correct, the ZW will be set to full power and then that power is stopped by the PowerMaster. The voltage is then increased and decreased in the PowerMaster (like a gas petal on a car) depending on values set in the legacy remote. It is like operating the ZW handles but via the Legacy remote. (Again the ZW handle is set to max and the PM does the rest)
2.) Add ERR Cruise to the engines to get effects similar to TMCC/Legacy. Now this is what I would definitely recommend, it saves you having buy the PM and you get the benefits of Cruise Speeds which makes a world of difference in my book. Some guys here swear by Conventional operation under the merits of KISS (Keep it simple S...) but I just like to keep all of my engines command controlled. That is my opinion and others will agree and disagree, that is the beauty of different experiences.
Let me know if you have any other questions Jeff!
Good Luck!