As far as I got the information. There are suggestions that the standard surface does not have an operating mode. This means that the pad will be fully compatible with Android and iOS. The Pro version will also come with desktop mode. Under normal conditions, "full Windows 8".
In this case, you can install and run Metro-specific applications on the standard, or better describe "Applications developed under WinRT". But with the Pro version, desktop applications for Windows are also available, such as classic Office, etc.
[UPDATE]
Based on several Microsoft QAs, they will make differences in versions of Windows 8. They will offer distribution of applications outside the store. This is an extremely important point, for example, for using business lines and for intranet purposes. Although, they are going to make it available for the Enterprise version of Windows 8.
". Only the corporate version of Windows 8 will be able to use Side Load applications. Side-loading bypasses the Windows Store before installing custom Enterprise applications in the organization .."
I feel the answer is a bit "Yes, you can distribute applications outside the store" and "No, for public or worldwide use, you need to go through the Windows Store." As a distributor, this seems to be a workaround. Although the recipients of this "side application" should be aware of this. This is a quote from the Microsoft developer page,
Preparing other PCs Some business users may not use a PC that supports sideloading. Common reasons for this are that the Windows edition that their use in the enterprise does not support this, or IT administrators do not control the PC. This scenario is becoming more common with the growing trend of personal devices used for work.
To enable the download of a Metro style application on a PC: Set the group policy to "Allow all trusted applications to install." if you cannot use group policy, then you can install it through the following installation: HKEY_LOCAL_MACHINE \ Software \ Policies \ Microsoft \ Windows \ Appx \ AllowAllTrustedApps = 1 Make sure the application is signed by a CA trusted by the target computers. Activate the special product key using the script on the target machine to enable the download. We’ll take a closer look at how the IT administrator will receive product keys in the upcoming Blog Post. The product key must be installed and activated once on the PC.
From the link: http://blogs.msdn.com/b/windowsstore/archive/2012/04/25/deploying-metro-style-apps-to-businesses.aspx
For business purposes, this is apparently a kind of package distribution in which you can choose which enterprise users should be acceptable, for which Windows 8 metro applications.