There is an error in your tutorial. VMPK can be used with Qsynth, but the instructions are wrong.
If you want to connect VMPK's MIDI OUT to Qsynth, then you need to select in MIDI Connections -> "MIDI OUT Driver" -> ALSA, and then select the qsynth client name in "Output MIDI Connection". Something like this:
On the other hand, the "Fluidsynth" output driver is an internal instance of the synthesizer that does not require qsynth (but you still need to install fluidsynth and soundfonts). The newer driver "SonivoxEAS" is another internal synthesizer not needing soundfonts at all and ready to use from scratch, so new installations of VMPK can produce noise at once.
There is an error in your tutorial. VMPK can be used with Qsynth, but the instructions are wrong. If you want to connect VMPK's MIDI OUT to Qsynth, then you need to select in MIDI Connections -> "MIDI OUT Driver" -> ALSA, and then select the qsynth client name in "Output MIDI Connection". Something like this:
On the other hand, the "Fluidsynth" output driver is an internal instance of the synthesizer that does not require qsynth (but you still need to install fluidsynth and soundfonts). The newer driver "SonivoxEAS" is another internal synthesizer not needing soundfonts at all and ready to use from scratch, so new installations of VMPK can produce noise at once.