Shredder recommends Systema hop up buckings for use with the SCS. Followed by Guarder clear (slicone) and Madbull Blue buckings. Systema buckings tend to work the best because they are thinner and take the shape of the SCS the best.
In my experience, the SCS tightens groupings a LOT more than tightbore does. However, you have to make sure it is installed correctly. If the SCS doesn't not sit level, it will make your accuracy suck. lol Once you get it level, it's amazing. Much better than an H nub. Some people have even gotten an fps increase with the SCS, which is kinda bizarre. Shredder does several videos where he chronoes with the hop up off and on. For some reason, with the SCS, the fps is increased by a lot. Usually the hop up lowers fps, by quite a bit too.
From what I've seen, the things that affect your accuracy the most are:
1. BBs are always the limiter. You can have the most amazing gun ever, but if you use crappy bbs, your accuracy will still suck.
2. Hop up set up
3. Barrel
4. Compression
This help any?