Yes.

The latter. It does not matter.

I am not sure what you mean by height but they are pretty much identical, only CSSU-T is built with an extra compilation option to generate the Thumb code. It also means that CSSU-T is always a step behind CSSU-Testing, as it always has to wait for any updates to appear in Testing first. However the delay is not usually that great and in any case, you get the Testing updates first anyway, only not compiled as Thumb. When they make it to the Thumb build, you get them again, slightly smaller. I hope I get myself clear, it's been a busy day.

Regarding the kernel, CSSU (any flavour) comes with its own kernel, unless you already have KP installed. If you intend to use KP, and I would wholeheartedly recommend so, then I suggest installing it first, before installing CSSU.