Actually, choosing "Selective Startup" in MSCONFIG and unchecking all the boxes will not (or at least should not) start Windows 98 in Safe Mode. What it will do is temporarily prevent your normal startup files from being read when Windows boots. This is different from Safe Mode in that required VxDs and other normal system level components
will load as usual. This is what M$ refers to as a "clean boot". So, for example, you can still access your CD-ROM drive, your network connection(s), and so on...very useful when troubleshooting; especially if you are having a problem that you suspect stems from a Real Mode driver, TSR or .INI setting.
Genuine Safe Mode uses a minimal set of drivers...meaning that most of your peripheral hardware (such as removable media drives, network adapters & protocols, audio hardware, etc.) will not function. This is also useful for troubleshooting when the issue is a Windows Protection Error, corrupted VxD, etc.
Sorry if this post comes off sounding like a lecture but I'm not teaching this semester so I'm probably stuck in "instructor mode".
I hope this info is useful in some way.
Chris