The guy in the video posted above is a serious IPSC competitor, and a competition gun would love those mods. If you aren't going to compete, you don't need all those.
When I bought my S2 and took it to the range in factory form, I hated it compared to my tuned SP-01 Shadow. When I got home I changed the mainspring, recoil spring, trigger return spring, (and pin), and firing pin spring. Then it was closer to what I wanted. The following day I finished off my first 1000 rounds, shot two matches that weekend, and then changed the disconnector the next day. Put another 1000 rounds through it, shot another two matches that weekend, and then more practice and matches. In the first three weeks I shot over 3500 rounds and it was getting broken in and feeling really good.
Others have installed a different hammer, shorter disco, or other bits, but I haven't bothered. Haven't felt a need. The gun, as-is, isn't holding me back. It's all me. lol!
Cajun makes good parts, and Eemann's are good too. There are others as well. Some site sponsors carry both those brands, and if there ever is a shortage in this country, you can order parts from Europe easily enough.