My desk is four poles and a slab of wood from Ikea. It has three 1920x1200 24" Dell monitors on it hooked up to a workstation beneath my desk. My chair is... I'm not sure what it is, but judging by the creaking and the claw marks, it's probably almost time for a new one.
I use a large/deep L-shaped desk, relatively high. L-shaped is best for me. I also use large desk mats for under keyboard and mouse.
I use 2x 4k monitors on solid midrange arms, with pistons being very useful for ergonomics, rotation is also essential for me. References on landscape screen, portrait on code screen.
I have had countless chairs. Key features: quality(hard to quantify, but chairs fail all the time), mesh is a must, needs good vertical height for ergo, order some roller blade wheels if you are on hard surface, and get one wheel with a lock on it.
I put a little piece of adhesive sandpaper/tractionpaper on the top of the spokes of my chair, keeps my feet from slipping off.
The cheaper full feature chairs on Amazon have failed on me after days before. ie plastic in the wrong places, metal bolts mounted in plastic that are load bearing, arms just falling off, mesh failing.
As much as it pains me to say it the Herman miller chairs really are very good. If you are in a big city, look for a office furniture recovery company, you can get a good deal, and they probably have a repair guy in house. These are usually in the warehouse district, they are great for pretty much your entire home office.
Final thing is find a good foot rest for under your desk. It can be anything that will stay put, doesn't need to be a "footrest". I use an old shoeshine box I found on ebay, it was the right height.
Desktop is a custom built rig, but also have a Thinkpad T480 for when I have to be mobile. The T480 is a great device, 1440p screen option and hotswapable batteries of differing sizes and great keyboard.
Nope, sorry; struggling with the right height myself at times I placed some (half read ;) books under the table legs. Being able to easily adjust the heights of both chair and table would be a good ergonomical feature. I guess it can be hard to find the right setup, just like finding the right bicycle geometry …
Depends on the card. Also depends on how many frames-per-second you're going for. A 60Hz refresh rate for four monitors is definitely doable with the right card, which works great for a work/productivity setup.
If you wanted something like 120hz or 144hz with four 4k monitors, you'd probably have a harder time finding a card that can push that many pixels at that refresh rate.
And yeah getting the right window/monitor setup is a whole process. Alt+F7 (at least on Linux) works to grab/move windows that get bumped off the screen.