It's pretty amazing that the article and the whole comment thread neglect OSes.
I use Debian with i3 on a 10 years old laptop with 4GB of RAM. It's my only workstation and I'm a software engineer.
I usually run two browsers including a tab for slack. Everything works fine.
Tip: install the documentation OS packages for all the libraries you need and also read manpages. Works well when you are on planes often and makes you a better developer than relying on search engines.
I'm not advocating for old hardware. (facepalm)
More tips: use powertop. Use CLI-based stuff. Download email locally in bulk/batches.
Don't use software that does home-calling or any other unnecessary network traffic.
1 large monitor is more efficient than a dual screen setup