Overall, Google Docs does a good job at converting documents into the listed formats. However, there is always a chance of losing some formatting, especially when switching from Google Docs to Microsoft Word. The same applies when converting a Google Doc to a Microsoft Word document when downloading.
If you're looking for the best way to send a Google Doc by email without formatting issues, opt for PDF. While the recipient can't edit the file, it should look exactly the same as if you'd printed it.
If you're uncertain about formatting issues, try sending the file to yourself or to an alternative email address first to check how it looks.