You are confusing terms and thus are getting contradictory answers. When you upgrade to Windows 10, you can do an upgrade or a clean install. An upgrade will update your existing Windows installation to Windows 10. Under this scenario, all applications and settings should migrate to Win10 without issue.
If you do a clean install, that typically means that the old OS drive is deleted and a new install of Windows 10 is installed. You will have to create your accounts again, install all of your applications and copy over any files that you want on the PC.