Feedback vs. volume
The rock guitar masters of the past got their signature tones using volume to drive the guitar - vibrating the body itself for enhanced sustain and controllable feedback. Modern guitarists try to recreate those classic tones at lower volumes. Some players go for lower volumes to remain on good terms with family and neighbors. Others seek a "classic" tone that they can use in small clubs.
Small-venue sound is an unusual phenomenon. If anything, live music is louder (on average) today than it was twenty or thirty years ago. Especially in smaller clubs. I went to stadium and outdoor concerts in the 1960s and 1970s that used less PA power than some of the small local clubs use today.
You can only push a small room to a certain point with a couple of 50- or 100-watt amps and a vocal PA, and the audience could always escape to a quieter location just by moving away from the stage. But with the drop in price of sound-reinfocement gear, even the smallest clubs can (and do) install multi-kilowatt PAs and drive the entire room to SPLs approaching (and in some cases exceeding) the threshold of pain.
The demand for lower stage volumes comes from the sound engineers (and I use that term generously) who want to minimize bleed from the stage so they can contol the FOH mix. The club is not interested in protecting the audience's hearing. If that was the intent, they'd ditch the lease on the PA, fire the sound guy, and rig a kill switch for the stage power so the bartender can shut down the band if they become objectionably loud at the back of the room.
It's true that some of the revered tones of the past depended upon volume-driven feedback. Nowadays, we often try to get the same effect at reduced volumes by using more gain. Unfortunately, that extra gain introduces compression which reduces or eliminates the dynamics that were also an important piece of those classic tones. The obvious (to me, anyhow) fix is to use a low-gain amp with a guitar that responds more to the room. That combination preserves dynamics (and the clarity that you simply can't get with cascading gain stages) and gives you controllable feedback at saner volumes.
A semi-hollow body electric guitar is ideal for getting sustain and feedback at moderate volumes. (Full hollowbody guitars - those without a center block - are not so good for this application. They have less coupling of the body to the neck, and are more inclined to "howl" as the body itself resonates without involving the strings.) Semi-hollow guitars are likely to be different from one another, so you'll have to learn how yours behaves by playing it at performance volumes. Some notes will feed back more easily than others - learn where they are on the neck and find ways to control them. A fingertip applied gently to a string right at the bridge can effectively control a note that's on the verge of feedback. Also, taking a step toward or away from your amp, or turning your body slightly, will affect how the guitar responds to the amp. This is something you have to develop a feel for - at first, the feedback might get out of control more than you'd like. Over time, you'll learn to anticipate and control the feedback.