More windows: ⌘N new window, ⇧⌘N new window from a copied link, right-click any link → Open in New Watch Box Window, or ⌘-click a link.

Just the picture: play a video, then ⌘E or 🎬 in the top bar. Drag the picture to move it. Back on its control bar brings the page back.

Arrange: ⌘T keep on top, ⌥⌘T tile all windows, ⌘W close.