The utility of a window manager like sway is stunted by many applications implementing their own window management facilities. Sway doesn't only support tiling windows, it also supports displaying multiple windows as a single window with a tab bar instead of a titlebar (or a similar mode with a vertically arranged tab bar). Any application that insists you use its built-in tab functionality is competing with sway over who gets to do window management, and it creates an awkward nested UI.
Sway is at its best when you take back control over window management from your applications and give it to your window manager. Firefox tabs are great, but they only manage Firefox windows. Tmux is great, but it only lets you tile terminals. Vim is great but it only lets you tile editors. This paradigm forces you to arrange your windows according to their type, rather than whatever layout makes sense for your workflow.
Here's a layout I often use:
I dedicate a workspace to writing a piece of software. I split it vertically and keep my editors for the files I'm actively working on on the right split and reference material on the left.
That means that my right split is mostly editor windows, but my left split is very heterogeneous. Sometimes I want to use a documentation web page for reference. Sometimes I want to reference a manpage in a terminal window. Or a repl. Or an editor window displaying a file in (conceptually) read-only mode. I keep all these sorts of windows in the same row of tabs — impossible in the conventional window management paradigm.
You need to choose software that lends itself well to this paradigm. Some software is more amenable, and some less.
Here are my recommendations:
Firefox with my webextension: https://github.com/adrusi/notable
Alacritty or st for the terminal
Kakoune for the editor (Vim probably can't be made to work, since it doesn't use a proper client/server model. Emacs doesn't work out of the box, but I'm sure it could be made to work. Atom and vscode conflate the concept of a window with the concept of a project too thoroughly for me to hold out any hope that they can be adapted easily. Kakoune works out of the box.)
Pidgin for instant messaging (works well for IRC and Facebook messages; has a config option to open new chats as new windows instead of tabs)
Zathura for viewing PDFs
Mpv for video and audio