Yeah, you have understood it right. Very good! Remember that those things are very simple and common sense and creativity can take you far, and of course you have to have hand skills, but those you can develop when you get experience working with iron.

A gasket is like a seal, it makes the connections so very tight that no leakage happens through. I haven't had in my bikes gaskets in lateral exhaust. The pipes has slid so deep and been so tighly tightened that no fumes has came out of other places except from where they are supposed to go out, and what is the easiest route from them to go out.

That your muffler seems to be iron, so it is easy to work with. You should consider opening your muffler and modding what is inside of it to get better gas flow and sounds. Maybe there are youtube videos or other articles to give you an idea what to do with the interiors of your muffler, which are again simple constructs, but a welding machine is a must.