First things first, I'm not much into Autechre (didn't listen much), am okay with BoC, and definitely into AFX.
I see a few differences between the gentlem3n and the gentlem4n, maybe detailing these will help understand how
a) their very overall style / aesthetic
The gentlem3n you mentioned, while differing amongst themselves, seem to generally stick around the 'electronic'
aesthetic and share a love for sine wave wizardry.
In contrast, Squarepusher is as much or even more jazz
than electronic. He started out as a bass guitar player, and a good portion of his works is literally drums and a bass (but so much more jazzy than the genre bearing that name).
The gentlem3n are fond of analog
tools, as those are essential for sine wave wizardry.
The gentlem4n seems indifferent
towards analog tools, partly because he does less sine wave wizardry, which brings me to
c) the focus (this is the main point)
The gentlem3n from what I know are mostly focused on the sound.
They try lots of little things, fiddle and tinker around to get the perfect sound, exactly how they want it. At light speed, too! Like an architect, they construct mathematically beautiful rhythm, melody, or the lack of those. To that end, they use whatever tool fits best, and perhaps even modify/hack the tools.
Squarepusher is all about the method.
Mostly in line with the jazz influence, he probably has no plan or idea how the music will sound like. He probably doesn't even care, either improvising or writing something "blind" first. What matters for him is how it is made - he's fascinated with abusing musical instruments and all the production tools. He's been writing his own music production software too. Very experimental; if there's a proper way to do something with an instrument; if there's an existing genre; if he did that in his previous albums; he avoids it. You could say that he's less interested in making music
than in making methods.
If you're not into jazz, I'm not sure if there's any good point of entry. In case you try, I would recommend following some sort of chronology, so you can perceive how things change. Now that I think of it, I clearly remember struggling with Squarepusher myself. When I first encountered his stuff, it pretty much sounded horrible, all of it. The only track I liked was "Tundra". But that track was so fuarrrking damn good, I could listen to it for hours. (I never once managed to sit through the whole track without my mind wandering off; it's magic.) YouTube eventually helped me a bit (Ernest Borgnine, Beep Street, and Feed Me Weird Things), and as I got used to the sound, he started to make sense.
You could also try sitting down on a chill afternoon, relaxed but not sleepy, and just listen to the entire Ultravisitor album with good equipment. If that doesn't hit home, he's probably not for you.magnet:?xt=urn:btih:3cf108e3c2f9e1b84284061968c40262820e75b0&dn=Squarepusher+Discography+%5BFLAC%5D+%5BDrum+%26amp%3B+Bass%2C+Acid%2C+IDM%5D&tr=udp%3A%2F%2Ftracker.leechers-paradise.org%3A6969&tr=udp%3A%2F%2Fzer0day.ch%3A1337&tr=udp%3A%2F%2Ftracker.coppersurfer.tk%3A6969&tr=udp%3A%2F%2Fpublic.popcorn-tracker.org%3A6969