Yes, regular ol' windows forms will work on Windows 8. They'll work on whatever operating system supports your target .NET Framework version. They may not run on the Windows RT tablet, but tablets running full Windows 8 will be fine.
There's no tablet emulator, but you can get Windows 8 running on an HP Slate 500, or (what I'm doing) run Windows 8 with touch control via Parallels on an iPad.
You can develop your app in Silverlight/WPF and have it work well in Windows 7 and 8, but also Windows RT (for ARM tablets). Or HTML5 apps are an option as well.