I've been using QWERTY with custom key mapped keys on my 75%, taking a page from the HHKB layout with the Capslock = Ctrl, \| = Backspace, Backspace = \|, as well as my right control key as a Fn layer key. [...] How I edit word documents now is that by holding down the right Control key (FN) with my thumb, I use my left hand on WASD to move around, and my right index finger on \| (Backspace) and right middle finger on Backspace (Del) to quickly edit documents.
[... definitely the best one out there]
Seems like you have a setup you like.
There’s absolutely no way that the standard keyboard layout (QWERTY/etc.), even with a bit of supplementation, is going to be the “best” for anything.
For English writing, there are many better alternatives for logical letter layout: Dvorak, Malt, Colemak, AdNW, etc. etc., take your pick, or make something new.
For programming, at the very least it’s essential to move common symbols off of the shifted number row, where they’re a slow pain to reach, e.g. by putting them on a shifted layer on the home row. That is, at least all of `~!@#$%^&*()-_+=]}\| should be moved elsewhere. The best specific place to move them all depends a bit on the programming language. (I also like adding convenient key bindings for greek letters, a variety of mathematical symbols, other types of punctuation, and so on, though these aren’t strictly necessary in the ASCII-centric programming world.)
For basic navigation and editing, the default keybindings in e.g. emacs (or dozens of alternative arrangements I can think of) are better than your proposed holding down of right fn + use of WASD with the left hand and backslash and forward delete keys for deleting. The WASD part is okay if a bit contrived, but the forward/backward delete would be much easier if moved to the home row, e.g. using J and K keys, or adopting emacs ctrl-H and ctrl-D. Your method requires moving your left hand entirely off the home row and twisting your wrist to hold the Fn key with your thumb while reaching your fingers up and to the left. This is both uncomfortable and slow for most people.
It’s fine if your delete setup works for you, but I wouldn’t recommend it for a general user. Any optimal layout is going to be built around a more rigorously defined system. I personally recommend using the same letter keys for both navigation and delete keys (the best definition for delete up and delete down are up for question, but they’re pretty useful, along with commands to delete to the beginning/end of a line, delete to beginning/end of a paragraph, or delete up/down by whole pages), on separate shifted layers, but there are other alternatives. Vim keyboard control for navigation and editing are of course several steps beyond any of these basic key bindings.
As for physical keyboard layout, standard row stagger / QWERTY is pretty bad. At the very least, splitting and separating or tenting and rotating the two halves of the keyboard makes for a big improvement. Adding a large number of extra thumb keys is also really nice. A "75%" doesn’t really solve any of the fundamental problems with the 19th century typewriter layout.
