It's good to move around a lot, yeah. But in a few years you will find that the position you sit does indeed matter. It's actually super easy to sit "correctly" in a chair though, to avoid the typical problems. I wish I learned it way earlier, because my posture is terrible as a result of my years and years of slouching in chairs at a computer for hours on end. I sat on a stupid wooden chair for most of my teenage years, for literally hours and hours -- and I never sat "correctly" in that chair.

Check out how these guys suggest to adjust their chair -- you can follow this with any adjustable chair and you will be 100% good to go IMO: https://www.hermanmiller.com/content/dam/hermanmiller/docume... (PDF)