Content will not be automatically published to the mobile website unless you explicitly configure it.
However, the overall content will be changed, of course, and as soon as someone decides to publish, the mobile site will be updated with content optimized for your PC site. For example: your PC site may have more room for text, so you may be tempted to create headings, etc., which are too large for your mobile site.
The main question is whether you can share content between two different media. Will the benefits of a simpler plan outweigh the potential conflicts? You will have to decide this for yourself.