Im no expert on the matter but I think performance difference between all mentioned options probably wont be noticable. If your cpu can handle fsb 533 than go for it, especially with your new ram(as for vcore bumping, its impossible to tell whether you will need it or not, you will find out when you do it and test for stability). My opinion is: 1:1 ratio+timings as tight as possible are most important, as you wont gain much with speed increase if you have to loosen the timings. I run my ram at 640Mhz(4-4-4-12) 1:1 with my fsb(320) because it feels more responsive than if i run it @800(5-5-5-18) via some funky ratio setting. If i run it at 980mhz (5-5-5-18) which is max it can handle, it seems the same as @ 640 with lower timings, but the sticks get really hot so i dont see a point. But if u want something to brag about, than go for higher numbers.
I would run with the 400fsb. I have no idea what mobo you have, but a 533fsb may not be attainable.
As for the memory ratios, it depends on how you use your computer. A 1:1 ratio with tight timings will give your computer that snappier feel, but at the cost of memory bandwidth. Which will slow you down a little in memory intense applications.