I modified the button according to your comments - should now behave like a normal toggle button until checked.
Also I decided to not modify the control template - thus now the shadow host is included. (I am currently on the verge on whether it looks better with or without it)
The style from #59 could be modified and used as a FlatToggleButton which would suit well if you dont want a border around the buttons (For example: UWP Command Bar)
I modified the button according to your comments - should now behave like a normal toggle button until checked.
Also I decided to not modify the control template - thus now the shadow host is included. (I am currently on the verge on whether it looks better with or without it)