Hi, and welcome
Yes we are trying to figure out the same thing (at least I am still trying to figure it out)! You pretty much have the thread summed up well. My aim is to feed a good protein source, like leftover meat, and filling the rest with sprouted/fermented grains. I just haven't been able to secure even bone/meat meal at a better price than feed, so I'm still only feeding fermented broiler feed. The fermentation helps with nutrient absorption, and also because it's wet feed they don't waste any by kicking it out of the feeder. Both these factors make the feed go further. It also ensures your meaties are getting a good amount of pro-biotics, which helps prevent disease.
I'm busy reading this thread:
https://www.backyardchickens.com/t/644300/fermenting-feed-for-meat-birds in which Beekissed shares a lot of great information on fermenting feed. I'm only on page 10 now and the page count on that thread is over 1500!!!!
However, from what I've read so far, it seems Beekissed only ferments whole grains for her meat birds without adding any additional protein. (What I've read so far was posted back in 2012, I haven't gotten to the recent stuff so I don't know if that's changed in the meantime). Seems fermentation is the way to go! Adding protein won't hurt of course.
Anyway, I suspect I'm rambling. About Barley being the best; I'm not sure. I have a lot to learn still! What I have discovered is that raising meat birds is not nearly as daunting or overwhelming as I thought it would be. I'm even considering raising 100 next time!