Sort of: Each instance has its own rules, admin(s), and may or may not federate with certain other instances. Some may also be more stable or responsive than others depending on hosting.

My broad advice is to avoid hexbear, lemmygrad, and lemmy.ml because they are full of tankies/trolls, other than that: Find the instance you like best and feel free to use more than one!

I’m on Mbin these days, but when I was on Lemmy regularly, I liked to favor instances that got their power from renewables