Think about all the time wasted time misclicking if there are individual buttons for everything which would by necessity be are tiny though. I’d say a version where everything has it’s own button and permanently displayed parameter value could well be visually slower to process and far more prone to errors, which would waste more time than a tiny delay in the buttons/precise values appearing.
I definitely feel at the moment there is a happy medium between. Tests such as the one you propose are subject to what the user is used to. It could well be that you are faster with the v6 mixer, where as I may be faster with the v7/8 mixer.