But fastest is only subjective to synthetic benchmarks. It's really hard to tell in real-life normal usage. And the split second isn't going to matter.
You can plug it into any port, but keep in mind that there is SATA 2 and SATA 3 ports. If you want the best performance, make sure you plug it into SATA 3.
Also note that even if you did have SATA Express on your motherboard you would need a SATA Express SSD to take advantage of the full speed.
But yea as ksham said make sure you are plugging it into a SATA III Port. The thing is though just for basic Windows usage you will see never little difference from using a SSD on SATA II VS SATA III...or well I haven't that is.