Earlier quoted context omitted.
Picture in picture was a feature I didn't know I wanted all along. I often had a window open only playing a youtube video, having it be native to the browser and always on top is such a great feature.
Open in new window. Resize window. Right-click title bar, select "Always on Top". App developers spend a lot of their time making up for the poor decisions of OS developers. A good window manager would give you tabs for free, PiP (aka an always-on-top window) for free, dark mode for free. Instead OS devs go overboard in simplifying things to the point that app devs have to pay the cost of delivering what users want.
With a proper PiP mode, that's no longer an issue.