Thanks, that is interesting to know. I don't like kimchi (it's just worse sauerkraut) but I ferment other things and I always wanted a fridge just for that. I didn't know these things existed.
In practice, you will get a poor result if you ferment at high temperature. Texture goes off first, but you can also get weird alcohols or formaldehyde forming.
From my experience, the lower the temperature (and the slower the fermentation), the more complex the flavor. This rule seems to hold for almost everything, from vegetables, to kombucha, to bread, etc. For beer, it depends what kind of beer you like. You can get very funky beers at high temperatures.