I've just read the entire thread and most people write "boil off rate".
Boil intensity is not the same as boil off rate. Those two are two different things.
For instance if you boil hard with your lid on, you'll notice the effects of a hard boil, but with little boil off rate. Like maillard products -> darkening of wort and thicker mouthfeel but also more coagulation of proteins and more aromas driven off.
If you boil weak, but with your lid completely off, you'll experience more evaporation than if you boil with your lid on. But you will not experience the effects of a hard boil.
You can replace "lid on/off" with lid partly on/ almost covered, if you want. It was just to get the point through.
My experiences from the last 6-8 batches with soft boil is more aroma is retained in the wort. More aroma from the hops, and more aroma and also taste from the malt.
But also a soft boil would mean that you'd maybe want to use more crystal malts for the mouthfeel, (uncoagulated proteins can only carry you a little bit of the way for mouthfeel), since the maillard products aren't as strong as they are in a vigorous boil. FG is also affected
slightly by a hard boil, you can end up higher. There's no caramelization occuring in the kettle since the temperature is to low for the volume boiled. It's maillard products.
Also there's heat stress. But I don't think that's something a homebrewer should need to worry about as a big brewery. Heat stress makes the product less stable on the shelf, and goes "bad" earlier. This is just something I've picked up in the litterature and podcasts and such.
A hard boil also picks up more oxygen which further darkens the wort and affects the fresh grainy flavor if good malts are used.
For DMS my experiences are that I've noticed it two times. 6.2% (ish) evaporation and a veeery gently simmer (I wanted to see how low I can go). Lid almost completely on, maybe an inch of opening. I did get DMS in a pilnser/wheat-grist beer where I fermented with us-05, but nothing in the same grist where I fermented with another yeast, it was a split batch. This happened twice. Two split batches. The two beers which didn't have DMS from the same split-batch had more vigorous fermentation.
Same setting on my induction plate with the lid 50% covered did not result in the same amount of DMS. I haven't been able to test this further since the ambient temperature did a nosedive the last week and my boil is weaker now comparing to what it was, so I had to bump from 4 to 5 on the induction top.
Hope this can help someone