Pretty much anything can be considered fair game thematically in power electronics, so there's no real "fringe" to speak of. There are releases dealing with everything from the sexual reproductive cycle of plants, to parental expectancy (Streetmeat), to gay rights (Straight Panic), male modeling (Live Sex Show), the world of high fashion (Mass Marriage), to taxes (a couple of Jim Haras-related projects)...you name it. The idea that power electronics generally has to follow some "extreme" political/social concept or sexual content in order to be defined as such is pretty silly, and although I'm a big fan of many projects that wallow in that particular trough, I'd hate to think of PE as limited to generally offensive or controversial topics.
Sound-wise, you could argue there's no real "fringe" to PE, either, since these types of boundaries are asking to be broken anyway. I've been actively searching for things that push the boundaries past the tried-and-true formulas for a couple of years, as well; here's what I've found:
Sick Seed - Finnish project running since around 2008ish. Takes a more "experimental" approach and the sonic structure is somewhere between actual songwriting and the simple layering formula of PE. Actual instruments play as big a role as obscure electronics devices and effects with junk percussion and feedback, and the more recent material pushes the musicality further while older material is more identifiable as PE, but still has a composed, rehearsed quality like any rock etc. Owes as much to no wave, very early industrial, and krautrock as it does the big-name PE greats (which as far as I know, Pekka isn't a big fan of, which speaks volumes). Lots of variation in subject matter; emphasis on speculation about future and the modern world, assessment of psychological and scientific matters, historical subjects, plus the perverse themes you know and love.
https://www.youtube.com/watch?v=7WCmqtaXPq4https://www.youtube.com/watch?v=ZGuY-VBSrT4Ultra - Long-gone "legendary" industrial/PE/krautrock/unclassifiable "band format" project of international collaborators. Sound incorporated a more psychedelic and less harsh use of electronics alongside instrumental pieces, tape manipulation/sound collages/sampling, and lots of absolutely deranged vocals that give William Bennett a run for his money. Went through two lineups and sound changed significantly between the late '90s and early '00s. Generally sleazy sexual subject matter, along with a healthy dose of satire, surrealism, and abstract nonsense. Absolutely everyone needs a copy of their "Delirious Elaborations" 4xCD box set from Dom America, which only costs a mere $20, and grants you access to really rare recordings of one of the best bands/projects of all time.
https://www.youtube.com/watch?v=O7YQhi8JwSUhttps://www.youtube.com/watch?v=xssAQuNqQLsHaus Arafna - Long-running German PE/industrial with a softer, more sensual edge to their sound and less overt presentation of various subject matter. Unfortunately I've just begun to familiarize myself, but they seem to be catching on with a lot of folks who aren't as comfortable with some of the "extremity" in other power electronics, to say the least. The duo are also a married couple, as far as I know, which reflects some of the "romantic" sensibilities of the project. I've also never really heard anything negative said about this project, which is rare in industrial etc., when you think about it.
https://www.youtube.com/watch?v=jKFqhIULLdohttps://www.youtube.com/watch?v=5Cd56P8I8_YPogrom - Relatively "extreme" PE from Lithuania that tends to challenge the boundaries of what PE is considered to be, alongside subject matter one might already expect from PE in general, mixing harsh noise, direct and straightforward power electronics, more experimental sounds, and sometimes even metal elements. Newer releases and more recent live performances feature a style of "singing" as well as more typical PE vocal delivery.
https://www.youtube.com/watch?v=9Y7nufucf5Qhttps://www.youtube.com/watch?v=Lq9pA335ZHUSutcliffe Jugend - Everyone already knows that this project began as some of the first UK teenage power electronics, but what they're doing today is arguably much more important. Tomkins and Taylor take a very advanced and musical approach to PE that is at once aggressive, cinematic, and emotional; with a sound that incorporates rock, industrial, PE, musique concrete, and what often feels like incidental film music. Their music also doesn't reference many external things, instead focusing on personal matters and a more intimate relationship with "typical" PE subject matter. These guys helped start power electronics, and now helped it to become something beyond what it's generally considered to be. If I had to compare them to any other band in the world, it'd be Swans, because they're just so much more than even the most accurate assessments of their sound and style can convey.
https://www.youtube.com/watch?v=n-BQdvUtmZohttps://www.youtube.com/watch?v=LL18PloXMmIConsumer Electronics - People are incredibly incensed (read: pissy) that the more recent CE lineup deviates from what they expect to be power electronics, and although I'm not always on board sonically, I like that Best, Froelich & Haswell don't care for that kind of opinion. There was actually a recent interview with Best where he mentions "sexist and misogynist" comments from people on this forum regarding his partner Sarah's membership in the project. If it can bother people that much that someone's vocals don't sound exactly like what you might expect, and others that that vocalist is female, that says more about folks' limited perceptions of what PE can and can't be than it does about Consumer Electronics, which I think people should take the time to judge for themselves.
https://www.youtube.com/watch?v=YsF5R2HWhC4https://www.youtube.com/watch?v=I69F8aWhatQPrurient - This project is pretty much ubiquitous with those into mainstream music that know about this kind of stuff nowadays. Translation is that hipsters find Purient especially accessible, for some reason, but would shit their pants if they knew about what was really behind some of this music. Prurient is considered "power electronics" but doesn't play by any conceivable rules, releases range from harsh noise, to power electronics, to more musique concrete territory, to lush cinematic techno like you hear on video game soundtracks. Not really my thing, but I can see why a lot of people really appreciate this kind of thing. The album "Cocaine Death" is pretty much essential.
https://www.youtube.com/watch?v=TMJ7i9d74REhttps://www.youtube.com/watch?v=5geog-nrXigThere are others, but I'm underexposed and too lazy to go looking. Hope that is along the lines of what you were asking. As you can see, more sensitive types and the tough-guy crowd alike tend to box PE into a formula of echoed vocals, flanged feedback, and synthesizer noise, but there's so much more to it than that.
