I haven't seen any benefit to disabling spread spectrum. If I disable spread spectrum, then I have issues with bluetooth and wireless intermittent disconnects. My SATA SSD bandwidth is also higher with spread spectrum enabled. So, from my perspective enabling spread spectrum is good, and disabling spread spectrum only brings bad. YMMV. I am not sure that there is any truth to the statement that spread spectrum causes stuttering. Especially, I think it is completely irrelevant to overclocking. If spread spectrum caused stuttering, it would happen at stock speed too, not just when overclocking. So, that seems like a myth to me.
I think turbo boost is based on Speedstep/Speedshift, so is required for turbo boost to work properly. I could be wrong. I use Speedstep. It's a great thing. I don't know why you would want to disable it. I mean, if you are setting world records and disabling it allows you a more stable last 50 MHz, sure, disable it. But for everyone else, leave it enabled. It saves a bunch of heat and electricity in the long run. And, it absolutely makes a huge difference in whether x.xx voltage is 'safe' vs not safe when overclocking. With Speedstep/Speedshift and C-states enabled, your CPU won't be pegged at full clocks and full voltage, which will allow you to more safely use those higher voltages only when needed, but drop down to lower voltages when not needed and extend the life of your CPU.