1. What if your user switches between computers? Cookies are no longer available, and they will be shown the tour again.
2. The difference is there would be a separation of concerns. The tour functionality should not be part of your app. It should be a separate layer.
3. The tour tooltips will take over the CSS styles of the bootstrap theme you are using. So all the fonts, colors, button styles etc. will be similar to those you are already using on your site.