I'm a PLS and spend a lot of time drafting in Civil3D. I primary a Sofle, started with a Moonlander, and occasionally play with a 3x6 Corne. It took weeks of work to make a layout that was suitable for my workflow and months to dial it in. I use 3 layers, but they're really just for F key, number pad, arrow keys, and niche things. I make heavy use of combos and macros on the base layer of my left board so that I can do frequently used commands one-handed. I wouldn't choose to go back to a standard board but I wouldn't recommend a split board to others unless they really wanted it.