In my case I've found niri's workflow quite nice for these scratch windows, since every new window opens to the immediate left of the currently focused window, and doesn't affect the size or tiling of any other windows, they're just shifted to the right.
That only works for windows that you would be opening and closing, not persistent ones like chat apps or music players?
Many of those apps minimise when closed and reopen when calling, so often it is not really an issue (although it's sometimes annoying that you have to specifically tell the apps to exit when you do want to close).