CAKEWALK STUDIO INSTRUMENTAL AS A VST OR NO?

There should be a few ways to do that. Try clicking the plus sign under File and see if you can insert an Instrument Track. If you can, do that and choose whatever soft synth you want, including studio instruments. This will insert a track that is a combination of midi and audio. You can edit data to like it was a midi track and the synth will play it. The track's OUTPUT has to be to the audio device you are using for playback.

Another way is to use the top menu to INSERT>Soft Synths>Studio Instruments (or whatever). A dialog box will open where you can select different options. Single Track Instrument will insert an instrument track. Midi Source and First Synth Audio Output will create a midi track and an audio track for the synth. The midi track will be output to the synth and the audio track will have the synth as its input. Midi data added to the midi track will play the synth.

Those three ways are the easiest ways to do it. I don't have that program but one very much like it and it should work the same.  I suggest reading your manual/help files for more information on using soft synths (VST/DXi). You can do a lot with them once you get the hang of it.