My arm rest mounting is very ghetto, I have basically tied the wrist rests on the moonlander to the arm rest
there are better mounting solutions available now, but I have yet to afford to invest in those, probably will in the future though
I have dedicated keys for left and right: shift, alt, control and windows, a waste kinda but it was easier for me, in the bottom outer corners where my muscle memory says they should be. The way to make them one shot modifiers is to search for OSM or one shot mod in Oryx, they won't let you use two at once though just one modifier, as when you click the next one that one shot triggers. If I have time and coding energy at some point I may try to alter how that works though (the firmware running on moonlander is open source so one can do some more advanced things there), so that modifiers optionally don't trigger one shot modifier's, that way one could just tap ctrl then alt then del to get that, but again that is not how they work right now
I don't think you can combine one shot modifier with having them overlap a key though, but if you compose one of those special keys that can do four different things maybe you can get something similar to happen.
I think but don't know for sure, that if you plug in a windows keyboard in mac its ctrl maps to cmd automatically, again I don't know that for sure.
Also I do like both one shot layer OSL and toggle tap TT for my layers, they work a bit different from each other, OSL if tapped let's you press one key on the layer and then jumps out, and if held acts like a modifier key that stays on while you hold it, so you can do things on the layer, while TT instead on tap switches to and from the layer, and on hold acts like a modifier to let you do things on the layer.
I think it is worth it to go through the list of options and try to figure out what each does and then also do check the options to see if there is something else you want to do too. OSL and OSM can both be made to toggle to a layer if tapped X times quickly, and then are supposed to let go when tapped once more.
Also I have set up layers with home row arrow and navigation keys, and mouse and wheel keys, so when I want to do navigating and editing I switch to my arrow layer, and when in no need for detailed mouse movement switch to the mouse layer, that latter one is very nice while reading articles/forums, as I have mouse wheel up down and left and right set up easily, no more reaching for trackball when not needing its precision and speed. Also home row on both sides, where for me both middle fingers move the cursor up ring fingers down and the left most and right most keys move left and right
mouse 1 over index finger, middle mouse for middle finger and ring finger right mouse, wheels are on row below with same direction as home keys. Wheels on arrow layer do home (left) end (right) and page up and page down for the up and down direction
also it is on those layers I hide some other seldom used keys like num lock, scroll lock, caps lock and pause break
Also my symbol layer also is my numpad layer where the numpad sits under the 789 keys. Then I have a function key layer with F1 to F10 under number keys and then further Fkeys on the rows below
All very nice things to have when needed
Also yeah agreed on the saving me from RSI thing, I was crying typing on my old keyboard, so I had to stop writing... that was when I pulled the trigger on moonlander as last hope to fix it, and it did, at least for typing
I also have the pdf on my computer with the 'printed' keyboard layout, and bookmark to it in my browser, so I can easily bring it up when I forget something
don't use that often though, but it happens.
But that is quite enough babbling from me for one post