II brew Hefes all the time, but I use 380. My experiences is that phenols are not as affected by pitchrate or temperature as the esters (isoamyl acetate/ banana most promiment). The reason I usually get «more» or «less» phenols is du to different mashing and fermentstion regimes which either produce more esters, which mask the phenols more (but the phenols are still there), or less esters which make the phenols stand out more.
An underpitch will give you some more esters, meaning not only banana, the bavarian yeasts are sturdy buggers, so they can handle a good underpitch, but you'll end up with more different esters in general, where some of them can bear signs of an unhealthy fermentation. Almost same as if you do a hermann verfahren mash, more different kinds of esters, without the "stress" though, but watch out not to get the bubblegum which in a traditional german weizen is a flaw.
The cleanest, by cleanest I mean the most balanced between isoamyl acetate and clove, and not much else which stick out much, are the beers fermented from a first gen yeast (not dry yeast) and kept at about 17-18c. You can get very interesting and flavorful hefes if you ferment higher, or even lower, or do a herrmann-mash, but the cleanest I've made are those fermented at the forementioned temperature. No need to underpitch or skip the o2. First gen usually gets you home.
But just to put things a bit in perspective regarding Gordon Strongs comment. The top placements in the german german homebrew competition a few years ago were all fermented at 22-23C as far as I remember. Theres a lot to process if one would dive into the making of bavarian hefeweizens.