I agree with you about multiple windows and it's the reason I changed to Cinnamon. I am completely lost when trying to work and handling multiple windows (file manager, 3x browsers, code editor, browser dev tools) at the same time.
I don't know if I'm missing something (If I am, please, please send me a link to a tutorial on it), but for now KDE and Cinnamon work for me, rather than against me.