Get a chair in which you can sit straight upright comfortably. No springy back, no ergonomic curves that your body will never fit perfectly. Every degree of recline will take one painfree year off your career. Trust me! You want the weight of your head balanced over your spine, look straight forward, shoulders relaxed while typing/mousing. Your eyes should be aligned at 1/3 of the way down your monitor because we have more visual resolution in the lower half of our field of view. A professional keyboard/mouse/trackpad tray is best to get the right alignment. You want the keyboard almost in your lap so you can type without tensing your shoulders. I prefer one big monitor with multiple desktops and possibly a KVM if you need to work on machines that are required to have air-gaps. With 2 monitors, you are always looking to the side, which isn't good over the long-haul. Keep your active work directly in front of you with secondary things to the side. Also get a second seat of either a ball or knee stool for some variety. Set an alarm every hour to switch seats. Just getting up and moving the seats is good for you. When the second seat gets uncomfortable, switch back until the next alarm. Keep lighting off to the side instead of overhead where it causes reflections and makes you need to crank up the monitor brightness.