Mark Spurrell is a Canadian tech YouTuber who knows a thing or two about building productive setups. His rig is geared toward getting things done. The mainstay is a 2020 27-inch iMac, a total workhorse of a machine.
He uses a sit-stand SmartDesk 2 by Autonomous. This desk is awesome for long grinds, because when he is bored of sitting, he can get new scenery with the click of a button. When he does sit down, he sits in a Kinn Chair, also made by Autonomous. This chair is basically an adapted Herman Miller Embody, the gold-standard of ergonomic office chairs. But at $419, it costs less than a third of the price.