The one app is i3wm. People say tiling wm do not help boost productivity, but it certainly did for me -- or at least I think that it did.
From hardware aspect (although it was never asked), I use a hhkb type-s with the hasu controller. You may think it's a small change, but the fact that you can remap the arrow keys to {h,j,k,l} also helps because you no longer need to stretch your arm to your arrow keys. It did cost a bit of money, but I'm happy that I have it. And aside from the arrow key remap, I also remapped other keys to help with basic functionalities.
T480s is great. (I think I got my config for around $1600 with deals -- i5 8250U, WQHD, 16GB RAM, 512GB SSD)
You could opt to get the IPS 1440P panel instead of the stock 1080P TN Panel (I'm not 100% positive if it's TN or IPS).
I think 8th gen i5 is sufficient for daily dev work.
The laptop keyboard is pretty decent compared to other brands (Dell XPS, HP Spectre, MAC, etc).
It does come with some flaws due to Lenovo's very bad quality control.
When I ordered my T480s, I had to exchange it due to very bad backlight bleeding that was worse than the normal circustances.
In terms of weight, it's pretty light, and is pretty good for travelling.
One of the other drawbacks of the T480s is that there is no official hard-shell casing. Honestly, I have no idea why some Thinkpad users have ideas against having a case on their Thinkpads, but I think it is totally viable to get one, as it would prolong the lifetime of the laptop unless you destroy it pretty hard.
I would opt to get the non-backlit keyboard, as I have 0 use cases when it comes to backlit keyboards. I think it gives a more sticky key feel to it as well.