65% gang
Being able to fiddle with your keyboard layout is part of the fun of mechanicals, I happen to have this remapped at the OS level, because even on a laptop keyboard (yes I have a physical escape key) it's more convenient 90% of the time to press left Alt than the reach my pinky all the way up into Esc land.
I tried gatteron yellow but too hard and gatteron red too soft ha.
While I'm not exactly sure what a 120% is (macro keys?) I've been looking for something like a gaming model with macro buttons on the left and / or on top, but otherwise 75%. Ideally split but single piece. Think MS Sculpt with extra buttons on the left. Haven't found one.
So I was contemplating building one, but I'd have no idea where to start. I've quickly browsed the reddit page, but in those parts they seem much more interested in very compact models.
Or, for a circuit board, it's probably easiest to find an open source design of a PCB, and figure out how you'd change it from there.
One thing you'd have to worry about is how to create a case for it. 3D print? Layer acrylic together? Re-use a standard size?
I don't know PCB design, so I think handwiring is the best bet for a first build. QMK has a handwire [1] guide, and I also use them for the microcontroller software.
Though for the build I'm working on now, I wanted a few extra features that would be hard to do purely handwiring (per-key RGB LED and hotswap), so I use a PCB designed to hold a single key [2]. It allows me to do custom layouts without learning PCB design, but it is a lot more work than handwiring. You would still have to build the matrix yourself like a handwire.
[1] https://docs.qmk.fm/#/hand_wire?id=hand-wiring-guide
[2] https://deskthority.net/viewtopic.php?f=7&t=11420&start=
I mostly built the 120% because it was quite a challenge to play Final Fantasy XIV on a compact split ergo. (And because my girlfriend gifted me a set of Evangelion keycaps and it felt like a huge shame not to use all 127 of them.) It was pretty much an excuse to fit all of the keycaps that I had into a mostly normal keyboard layout. The extra keys are things like F13-F24 (poor OS support on those but I remap them to useful shortcuts for FFXIV with AutoHotkey), media controls, a language switcher, stuff like that.
If you want to try your hand at creating your own designs, it's actually not that hard to get started in my opinion, at least from a hardware perspective. I went from never having soldered or 3d printed before to typing on a working keyboard in the space of a weekend hackathon. All you need is the electronics hardware (microcontroller, keyswitches, keycaps, diodes, wire) and some form of keyplate and support. I would recommend lasercut acrylic since it's not very hard to get started with the 2d design with a variety of software options. If you have 3D printing experience and access to a printer then that might be quicker and more convenient.
I have a few designs on GitHub if you want to take a look:
The Sandiego [1] was my first design and so the firmware is pretty simple, so it might be an okay starting point there. I used OpenSCAD for the keyplate design and didn't make a case ever. There were wires hanging everywhere and it was a guaranteed conversation starter at work. Entirely handwired, so no PCB design either.
The Sigmar [2] has a keyplate and case designed in SolveSpace, which worked ok but it was a bit tedious. For this sort of 2D design, I think it was overkill. I used QMK for the firmware, which was kind of a pain in the ass to be honest. I probably wouldn't use it again. You get a lot of features built in for free though, which is definitely a selling point. I did a PCB design in KiCAD and I would absolutely recommend doing the same for your second keyboard. (Wire one by hand first!)
The Type K [3] is the 120%. Did the keyplate and case design in straight Python, generating DXF files for lasercutting. (I made a few mistakes in the design which I had to bodge with a bit of drilling...) The firmware is a beast because it has no dependencies on any USB libraries or anything. Wouldn't recommend that route unless you were seriously interested in USB, but it was definitely educational. PCB design again in KiCAD.
[1] https://github.com/smrq/sandiego/tree/v1
Why do you go on the internet and ask aggressive questions predicated on a wrong premise? Just out of curiousity.
I assembled many model kits and it never occurred to call myself a builder. Model kit builder concieve the kits and or create parts out of raw material, epoxy putty and/or 3d printing.
Similarly a bicycle builder will solder/bond individual tubes to build custom frame and fork, possibly custom stem and/or racks. A brand that source frame builts in Asia will but mount the ready made part will say "assembled in <insert the country>.
Maybe I am picky with semantics but it strikes me as arrangant to call ourself builders when we just pick up and assemble parts.
You can "build" a PC or a bicycle without creating any custom part, but the end result will be unique. A keyboard has less parts(board, switches, keycaps and maybe a controller) but I think it still count as built.
If you order everything as part of one kit, like the furniture from Ikea, then yes, you just assembling it together.
There's no ambiguity here, the hobby is called model building.