It’s true we can infer a lot of what it looks like from what we can see and using data from other galaxies. However that does often change. I’m not even sure which is the more current version right now, but here’s another version with four more pronounced arms. The same original arms are there, but the others are more dust and different star makeup than the first and could be more pronounced than once thought. There are also several different structural wave patterns rippling through the galaxy as it rotates.