Initial tests are positive, I think I am on to something with this multi-arm idea:
Laptop and monitor on arms. And yes, dang it, a third arm is on its way for the secondary monitor.
The monitor arm is not all that visible in the first photo, so here is a better look:
The laptop tray
The "tray" the laptop sits on has easily adjustable "legs" and is screwed on to the VESA mount. The laptop itself just sits in the tray. A strap was included to attach like a belt or something across the top of the laptop if you want it to sit sturdier. I guess you want that if you tilt the laptop and stand a lot to get the screen angle you want? Otherwise, I have a hard time seeing how a laptop could fall out of this arrangement without an earthquake or something similar.
I have adjusted the leg length to fit my 15" work laptop, so with my Macbook air there is a bit of a gap sideways. Should that start to bother me, the legs have thumbscrews and so would be quick to re-adjust on each laptop change. There, I just did it.
The arm itself
The arm itself is a Deltaco thing. It does not feel quite as sturdy and industrial as my old Multibrackets arm, but that is not automatically a bad thing. The Multibrackets is so sturdy that it is sometimes a bit hard and unwieldy to work with or adjust. Setting up the Deltaco was quick and painless, and all I needed to do except attaching the desk clamp and mounting on my desk was adjust the arm resistance a bit to suit the weight of my laptops.
So far so good. The real question is of course if the arm will hold up as well over time. My Multibrackets arm has performed like a champ, is on its seventh year and shows no indications of tiring. I will set a timer (no I will not) and report back on the Deltaco in 2029.
Desk situation
The cable situation remains a bit of a mess, and will get slightly worse when I need to sneak another display cable (plus power) into the situation, but it already feels really nice to have cleaned up space for keyboard and pointing device. And to have the laptop screen at somewhat more of the same level as the main one.
Yes, it also feels really good to be back on a mechanical keyboard sort of by default. I do not feel faster, but many things are so much more convenient, including having my hands farther apart. Plus, I feel somewhat … cooler? More down to business?
Who cares, the real point is that it is both fun and makes my main work station that little bit more fit for my purposes. Putting effort into making your main workplace feel more just so for you is probably always a good return on investment. I think that would hold even if you were to actually make it worse in absolute terms - as long as you made the change in a way you felt like you would probably feel better about your work and therefore also do better work.