more string section

On X1 I see "SI-String Section" in the VST plugin list. I believe that is part of the "Studio Instruments" package.

It doesn't matter.

The SI range of Cakewalk vsti's was introduced, I think, for X1 and haven't been changed for X2

The dll's for all the SI range at least for 64 bit, are installed under their own names in C:\Program Files\Cakewalk\Vstplugins. There is a folder for each one Bass Guitar, Drum Kit, Electric Piano, String Section

For 32 bit systems the dll's should be under C:\Program Files (x86)\Cakewalk\Vstplugins.

I'm not entirely sure what you mean by "not listed in VST plugins or anywhere else"