That “audio” meter is the CPU meter in Logic. You’ll just have to take my word on that if you aren’t familiar with Logic. In Logic it has one meter per CPU core.
The instrument tracks make it so I can use the CC121 to adjust EQ and sends when I have the track selected. That doesn’t work if you use the VST Instrument rack. Also the nice thing with instrument tracks is that they will be in the same order in both the arrange and mixer windows.