I ride in ChampSys kit as it is my club supplier, my opinion is mixed and only based on the kit I have or have seen in the flesh. Since buying my kit, new kit has been released with more technical features so some of what I say below may have been addressed in newer iterations. As a company, they do as they say they will and are reliable when it comes to delivery deadlines, unlike other companies.
The shorts are a nice material and look good but IMO they rely too much on tight leg grippers, rather than good design to stay in place, this means that even those with skinny legs (like me) will find them tight, lots of people say the same thing. The legs are also reasonable short.
The jerseys are okay as far as a standard jersey goes, no different to any other £30 jersey tbh, the colour and printing was high quality. The race fit jersey was not short enough in the front for me so bunches up when on the bike and there is no silicon around the bottom so the jersey rides up, the fit is okay other than that, but with the jersey not being stretchy, the fit is what it is and you can't really size down for a skin tight fit and I find there is extra room at the front of the shoulders on me.
The speeduits look great to me and fit those who use them very well, I will eventually purchase one.
The skinsuits similar to the above, quite stretchy so you can size down, but will probably have the leg gripper being tight.
Winter jacket/jersey, brilliant, it is very warm and also nice and stretchy, so can size down for a nice tight fit.
As for whether to go for standard kit or upgrade, what exactly do you mean? If you mean the chamois, I would say the endurance model is better than the performance model, not much difference when you 1st buy them, but the performance one seems to go flat/lose the padding effect over time, the endurance model holds up well.