I have never touched the film/exposure to set anything. Only color management/exposure. There is no manual setting in my version of Photographer addon that adjusts film/exposure. If you use Nishita sun & sky texture at strength 1, that is your reference light. My version may be outdated, but when I set sunny/16 rule (f/16, 1/100s, iso100), Photographer sets the film/exposure to -6.64, and anything under direct frontal clear sun & sky light should not be overexposed. I think mine gets underexposed, but I think I used a version pre Nishita where other assumptions were made.
The issue is that in vanilla Blender nothing (yet) is measured in photometric units (nor can we measure received light), but in some “weird” watt measurement that has nothing to do with a lamps electrical watt usage - this “watt” term has caused insane amounts of confusion. There is an addon that gives you extra lights in the light menu, the free one does come with a few reference lights that provide a good enough starting point for almost anything artificial (not LPS or other “pure” sources, Cycles can’t do those). An 800 Lumen A19 LED lamp translates to 2.1308 watts.
In real life you can capture a lot of exposures and assemble them into an HDR and work from there. In rendering, you get everything there is in a single render as long as you save in some HDR format and work from there. The most common and no brainer approach is to use filmic - it simulates more how a analogue film emulsion camera works, in that more bright actually appear more bright, at the loss of saturation. The next thing is tone mapping, which you can do in blender or externally although I could never get acceptable results (I know it can be done) and use sRGB instead of filmic. While some may want to go ACES and apply LUTs, corrections, and other grade work in i.e. DaVinci Resolve (too complex pipeline for me, but I don’t do things for “art” either). Personally I just use filmic and call it a day, it works for my purposes and I don’t have to involve my brain.