dactyl-manuform-keymap VS graphite-layout

Regarding chording, you might find inspiration in the chording schemes in Ikcelaks’ Magic Sturdy, the Ardux project, and precondition's "steno-lite" combos.

I spent most of the last 2 years using variants of this but more recently I’ve switch from home row mods to one shot mods and modifier positions similar to Xah. https://github.com/precondition/dactyl-manuform-keymap

Something that made a big difference for me was home row mods. If you can use QMK to embed ctrl, shift, alt, gui into ‘long press’ on the home row it will reduce strain from overusing the pinky finger. After about 1 year of using a variation of this setup I think home row mods reducing pinky finger strain has been the most noticeable improvement although there are many more benefits to switching to something like this dactyl manuform kb. https://github.com/precondition/dactyl-manuform-keymap

How did I arrive to this keymap? It's been a journey. I used home row mods for a few months. This felt great, but with my sloppy typing I routinely got false triggers (despite IGNORE_MOD_TAP_INTERRUPT) and struggled to get my typing speed much above 60 wpm. ​In an attempt to reduce false triggers, I wrote my own (not very good) mod-tap implementation, then realized this is a hard problem. I tried Precondition "steno lite" (see the system of combos in his keymap), and worked through some lessons from Zack Brown's excellent Learn Plover site to learn a little about real steno. I've dabbled with RSTHD and BEAKL15 before going back to Dvorak.

I have a few layouts and can't choose between them but I am also free to other options. How to choose the best keyboard layout for the matrix keyboard (Moonlander)? I was considering: Graphite, Gallium, and CTGAP

Keyboard layouts that are worth checking out are Canary, Graphite and Semimak. From what I understand they have all been made in the last two years. I'm biased in favor of Canary as it's very similar to Colemak which made the switch easy for me and I find it really comfortable, but the only thing that really matters is your personal experience when actually typing on the layout, not all the statistics that some people obsess over endlessly.

I suspect you have been researching this a lot and have seen it already, but I'd look at the Graphite layout and the Nerps layout as good modern "alternation" focused layouts.

I think the fact these are the only painpoints is also its selling point however, everything else felt pretty great. The ji, column my analyzer came up with took a bit of time to get used to but felt really great after a while (now also found in Graphite which I think is also really good). Both pinkies feel good in fact, and the vowel setup works really well. I alted dy, nothing else really felt worth it. lr middle is not a lot of usage for what that finger can handle but it allows str to be one stroke rather than a redirect (if you were to swap middle and ring which I don't think is quite as good).