What is the BEST office/computer chair out there? Herman Miller Aeron? Steelcase Leap? Or a different brand?

I’m not sure as far as the brand goes, but if you’re planning on spending a lot of time in it I reccommend a good quality task chair. They’re meant for long use and adjust to your comfort zone. I worked at a call center and the whole place was filled with task chairs so that it was comfortable to sit in them 8 hours a day. You can find them at any local office supply store (Staples, Quill etc.)