There are many issues in transferring files between machines with different OSes; file paths are different, many apps install only files needed by the installed OS so moving it to a machine with another OS will break it. Some files, such as application config and installers, are hidden but can be migrated to new machines. Other files, such as application caches and registry settings, are machine or user specific and cannot be migrated, and it is not obvious which are which. Do not try to copy files manually.
The Windows Easy Transfer app will migrate user data and documents. The Windows User State Migration Tool can migrate some application settings to a new machine.