Each manufacturer builds different RAM modules with different specs.
Not all DDR2 533 modules run at the same exact timings but you should expect something like 4-4-4-12 at 533 MHz.
Of course, you might be able to tighten the timings if you increase memory voltage.
Don't exceed 2.0V though unless your manufacturer specifically indicates that you can set higher voltages.
When it comes to timings, the lower the better.
It depends on the memory...for some reason my value DDR2-400 can run overclocked to 533 with 3-3-3-5 timings. The only way to find out is trial and error
Well, it depends on the change. For instance, going from 3-3-3-8 to 2-3-3-8 will have negliable differences, except in benchmarks. Going from 5-5-5-15 to 3-3-3-10 would have some noticable changes.
As was mentioned, each RAM stick is different. So you have to just try and see what you can get. You may have to run looser timings than you would normally like to get your CPU to clock higher. That's a choice you have to make. Is 1 point faster CAS better than 500Mhz on your CPU? What about if it was only 250Mhz?
IMHO, "good" DDR2 timings are equal to "average" timings on DDR sticks. So, if you can get a DDR2 stick to run at 3-3-3-8 and have a healthy OC, then that's pretty good. Anything lower than that is great.
I seem to recall that Corsair warrenties it's DDR2 modules for up to 2.2 or 2.3 volts, so double check with your manufacturer.