Intel Turbo

It says on Steinberg website to turn of Turbo boost, Why should I not put this on? Surely more GHZ=faster?

You can try keeping it on, depends on CPU and chipset. It might work on the newer i7
But in general to ensure a stable performance that is not interrupted by the CPU clocking up and down.
On my now older 3770k I had to disable it or I would get spikes in Cubase. I set it to a permanent overclocked state instead.