I hesitate to recommend a YT source because we know what most of those are worth. But Rick Beato (and Rhett Shull) have a huge following. And I find that a lot of their videos are, at a minimum interesting, and some educational.

They, and Dave Onorato and Ken "Grand" Lanyon produced this very unscientific study of the sound with lighter strings, titled "You’re Probably Using The WRONG Guitar Strings". Dave Onorato is a well know guitar tech. I'm not sure tabout Lanyon.

Here's the link: You’re Probably Using The WRONG Guitar Strings

I did not realize until seeing this that almost all rock guys used lighter strings "back in the day", the "Golden Age of Classic Rock" as you called it. I subscribed to the theory that one goes to thicker strings for tone. And that SRV did so. But as this video claims even he went to lighter strings not long before his death.

Without any intention of it being permanent I went to 9's on a couple guitars when I started working on bending. A year or more ago. I would use those guitars for bending. It was easier to bend and my thought process was that after I build up some finger strength I'll go back to larger guage. But then it occurred to me it didn't seem that I wasn't giving up any tone. I went to 9's on a couple more.

Now I am completely rethinking whether I'll ever return to thicker guage. I don't know.

Thanks for starting what I think will be an interesting conversation. I'm interested in what others here, especially some of the instructors, will have to say.

btw, I don't know if it is true but I read that BB King posed that question, "Why work so hard?", to Carlos Santana.