I recently was shopping for a new chair for home, and realized that... I don't actually need anything special because I habitually sit on the front half of the chair and don't rest my back against the back. So I just got one of the low-tier Steelcase chairs we have at the office and it's great! It'll last, and it's just... fine.

I tried sitting on a yoga ball for a while, but realized that it's not doing anything more for my back (because of how I already sit), but it's difficult to turn between my three laptops because the ball sticks to the floor and my clothes. So I went back to the chair. <shrug>

Yes, the yoga ball helps somewhat but it is a training tool not a permanent solution as it is quite awkward to sit on. I've been there long time ago, it was recommended by a chiropractor. I used to have bad issues and was seeing a chiropractor 20 years ago but am doing really well now. As a matter of fact I'm in much better shape in my 40s than I was in my 20s and I don't work out like crazy. It was all about fixing sitting/standing and walking postures then the benefits became apparent. You seem like you're on the right path or even are in good shape yourself. Leaning on the back of the chair or supporting on the armrests teaches us to sit wrong and while maybe comfortable at the time it will soon start to mess up with the sitting posture. And sitting on the front side of the chair is a good way to sit. Also I find that bringing the keyboard as close as possible to the lap and the body (desk or keyboard extender) promotes good posture. (elbows close to the torso and body straight, head above torso not sticking out front, adjusting the screen at eye level helps with that).

That's honestly pretty much how I sit, so it's good to hear. I've got a very particular setup that's comfortable to be at and work at for a while, and then I can raise the desk (standing position) because that makes me feel good too.

I do a fair bit of cycling and every-other-day core workouts that are kinda needed because cycling makes my hamstrings and lower back tight. It all happens to come together and I feel the same as you, much better shape in my 40s than my 20s.

I might dare to say I feel pretty darn good physically, most of the time. And can even push myself to pretty hard points (where things hurt, but not in an injury type of way) when I want. I hope I can keep this up, but sort of feel like a bunch of good practices that already are in place can lead to that.

Link?

I kinda meant a link to information about the proper posture and exercises you mention.

Also curious

Curious about what? Proper posture?