Quiver supports live preview of Markdown and LaTeX cells. You can switch to Side-by-Side Preview (⌘6) to see the editor and preview side-by-side.
You can also double click on a note in the note list to open it in a new window, then switch to Side-by-Side Preview. You will see something like this:
When you make changes in the editor, the preview is updated as you type.
By default, scrolling is synchronized between the editor and preview. But you can turn this feature off in the View Menu > Note View > Scroll Sync.