There are “Inst” and “Pad_sum”.
I can see the difference in Track controls settings.
But I don’t know Why.
The first one has enabled automation.
It is a matter of Cubase automatically wrapping the track control elements.
Your “Inst” track is set to display a VST parameter that allows only an on/off value and thus is displayed as a power switch.
The “Pad_sum” track needs more space to display the value of the selected parameter.
Okay, I got it.
It is a matter of difference between “Volume” and “Mute”.
Hi,
I want to jump into this game of searching for differences… 
You can click on the parameter and select which automation parameter is shown on the track. By default, the Volume parameter is selected if you create a new Group Channel. You can also open another automation track under the Group Track, same as you do for any other track type.