Can I safely overwrite existing ADMX templates?

I recently changed the storage for ADMX files into sysvol\domain\Policies\PolicyDefinitions and downloaded Administrative Templates (.admx) for Windows 8.1 and Windows Server 2012 R2 fromhttp://www.microsoft.com/en-us/download/details.aspx?id=41193

Now I wonder if I can:

• overwrite the existing ADMX templates with the new ones? Server is a 2008 Standard.
• Will this affect Group Policies in use or work as before?

Thanks in advance.