So the tutorial I was looking at was for using plasma as the compositor for i3. I couldn't get that to work, nor was it what I was looking for. All I had to do was install sway and I could pick it from the login screen!
I need to remember what's a compositor, what's a wm and what's a desktop enviroment at each step of the process. A lot to juggle there.
*Fairly quickly, if I can figure out how to log out from within sway.
just exiting sway does it! Now I'm cooking with gas.
I did all this mostly so konqueror / dolphin would have icons and such without having to manually configure. It seems the dark color pallete bugged out and only partially applied. I suppose with both kwin and sway switchable fairly quickly, that's fine.