If you pin your active note, any further note will be opened in a new pane. In addition, you can split the current pane in half either horizontally or vertically. Do this with the menu at the top right of the pane, use the command palette, or set a Keyboard shortcut.
Yes
I haven’t worked with multiple monitors yet so I can’t share any experience. But I guess you can open the same vault twice - and then move one window to your second monitor.