You are asking a simple question that has a complicated answer.
I will try to mention the various considerations, but a deep dive is a subject for a full book.
First of all, you are looking at sound regulations of the venue. Some venues have a maximum sound level that you must abide by, so that blocks you in on the high volume end. The flip side is that the quietest your show can be is determined by the ambient noise in the room - the sounds of the HVAC, the white noise of machinery, etc has to be covered by the sound (sometimes shows even turn off a/c during quiet moments).
Those things set the dynamic range of your show.
From there it is a matter of style, taste, and desired effect. Modern audiences are used to blasting headphones and TVs and going to loud concerts and movies, so they expect the sound to come TO them, rather than being active listeners, so there is a tendency for shows to lean 'loud', while some directors and designs actively try to push back against that by keeping the show quieter intentionally.
Of course, ALL of that then has the wrench of a live audience thrown in. Attendance of a specific performance makes the sound vary quite a bit. When an audience is more full, their bodies soak up some of the sound where as an empty audience can make a show seem louder because the sound has more hard surfaces to bounce off of.