it shouldn't actually matter, but you might need to download steam from steam (or check what your package manager is serving to make sure it's the runtime client and not the native client)
idr what the runtime/native client difference is, but i just know runtime has another abstraction layer that helps with compatability.
if it ends up mattering, I'm running wayland.
and beware, while not really that big of a deal, manjaro does require either a bit more nuts and bolts linux knowledge (or at least, an idea of what to Google, which isn't that high of a bar), and a willingness to be frustrated, because it pushes updates to apps as they happen, which can sometimes break others. It happens less these days, though. it's also based on arch, so the arch wiki doesn't need translation.
Most other distributions are slower, so they can try and get everything as compatible as possible before sending the update.