To answer your question about launchers:
Yes, they are like explorer.exe on Windows. Most launchers will replace the home screens and app-launching window. Some may even affect the app-switching, but you might have to play around with them.
A short list (note: not complete) of Alternative Launcher apps:
- Nova Launcher
- ADWLauncher / ADWLauncher EX (Paid)
- Go Launcher EX
- LauncherPro / LauncherPro Plus Unlocker (Paid)
Looking at the above apps you can see how they change the look-and-feel of the bulk of Android's UI.
I have tried most of the above, and each have extensive options and tweaking abilities to get your home screens and app launchers to look the way you want them.