So for me, my layout preferences are a constantly evolving thing, iterating on what I like, and removing what I don't. My current daily driver.

It's a new Clueboard v4. I've been really liking the Clueboard for the 'superplate'.
Going a bit into the plate and its purpose: The plate is what holds the switches in place and can be made out of many different materials, and be mounted in many different ways. You don't actually need a plate- you can use PCB mount switches and mount them directly to the PCB. The result is a bit too bouncy for my case, and with how heavily I type, I just don't trust it- though there's really no evidence to support my lack of trust, in all honesty. But the plate can be aluminum, carbon fiber, steel, brass, bronze - or really any semi-rigid metal - with varying degrees of support, resistance, and aesthetic appeal. Similarly, there are many different ways to mount the plate in the case- the simplest being a sandwich case, where the plate forms the top. There are also tray mount, bottom mount, and top mount variations. The super plate is a combination of the top part of the case and the plate. I really like the support it gives (did I mention that I type hard?) and the feel of the mounted switches.
You can see the detail in the following image:

On to the layout- my current layout is merely an iteration on my prior ones, now having a split right shift, a split space, and a maximized bottom row. My layers are set up as shown in the images below:
I haven't assigned the extra spacebar to anything but a spacebar yet; I've been trying it out, to make sure that I don't hit it in normal practice as I theorized. If I don't, I'll probably make it backspace or enter, and hit it with my other thumb to reduce travel.
It's a really interesting hobby- and I do believe it has increased my typing speed and accuracy, and my overall productivity. I can measure the first two, but sadly, the only measure I have of the last is my work, and considering that it's just changed a bit in scope, I don't really have a good measure.
Ask any question that you will, and I'll try to answer
