[T-Mobile Samsung Galaxy S II SGH-T989] car vs driver:
It was compiled specificaly for the SR. While all configs were set for both the SR and SII, it would likely need to be tweaked a bit for any SII needs by another developer.

Standard Disclaimer: Anytime you over clock a chip, it will reduce its life expectancy. That's just how it goes. But, with that being sad, the GPU is overclocked about 30% (300/228) more than stock and I have seen no problems with that on the SR so far. When I clocked it up to 320/266 it started complaining, so I didn't release that version (but you can compile it that way if you know where the setting is).

Negative. Right now you can only do that by swapping out the kernel. I had a lot of problems when trying to allow for it to change via script or some other means. I'm still working on making that happen, likely in the next release of the kernel. But that'll be a while since I'm taking at least the next few days off from development over Christmas to just chill with my family.

Or ... you can try doing it with an init.d script, something like the following. I couldn't get the settings to stick on my device, so I'm probably missing something somewhere. You'll need to know how to put the following code snippits into a script. But this should be enough to get you started. The directory path is for the SR, not sure if there's a difference on the SII though.

This is stock:

echo 266667000 > /sys/devices/platform/kgsl-3d0.0/kgsl/kgsl-3d0/max_gpuclk
echo 266667000 > /sys/devices/platform/kgsl-3d0.0/kgsl/kgsl-3d0/gpuclk

echo 200000000 > /sys/devices/platform/kgsl-2d0.0/kgsl/kgsl-2d0/max_gpuclk
echo 200000000 > /sys/devices/platform/kgsl-2d1.1/kgsl/kgsl-2d1/gpuclk

echo 200000000 > /sys/devices/platform/kgsl-2d1.1/kgsl/kgsl-2d1/max_gpuclk
echo 200000000 > /sys/devices/platform/kgsl-2d1.1/kgsl/kgsl-2d1/gpuclk

This will overclock you slightly:

echo 300000000 > /sys/devices/platform/kgsl-3d0.0/kgsl/kgsl-3d0/gpuclk

echo 228571000 > /sys/devices/platform/kgsl-2d0.0/kgsl/kgsl-2d0/max_gpuclk
echo 228571000 > /sys/devices/platform/kgsl-2d1.1/kgsl/kgsl-2d1/gpuclk

echo 228571000 > /sys/devices/platform/kgsl-2d1.1/kgsl/kgsl-2d1/max_gpuclk
echo 228571000 > /sys/devices/platform/kgsl-2d1.1/kgsl/kgsl-2d1/gpuclk

This will make your GPU piss fire ...

echo 320000000 > /sys/devices/platform/kgsl-3d0.0/kgsl/kgsl-3d0/gpuclk

echo 266667000 > /sys/devices/platform/kgsl-2d0.0/kgsl/kgsl-2d0/max_gpuclk
echo 266667000 > /sys/devices/platform/kgsl-2d1.1/kgsl/kgsl-2d1/gpuclk

echo 266667000 > /sys/devices/platform/kgsl-2d1.1/kgsl/kgsl-2d1/max_gpuclk
echo 266667000 > /sys/devices/platform/kgsl-2d1.1/kgsl/kgsl-2d1/gpuclk

As far as the CPU cores being very active, there's a reason for that. In this kernel, I implemented ARM big.LITTLE processing topology (similar in nature to what the Cortex-A7 & Cortex-A15 combination gets for you - hence the name). Basically, this promotes second core usage to actually improve battery life and performance. In short, the system will choose the optimal core for a given task to process and seamlesly swap between the two. This promotes efficiency and you will see the second core more active as a result. Without this, the first core becomes a bottle neck, maxes out and then the second core comes in and starts ramping up immediately to satisify the additional work.

Oh, one more thing ...

You will always see time on 1.512, even if you max CPU is set less than that. The kernel immediately hits that frequency during boot to speed it up, after which it will pay attention to your settings.