Their exchange isn't worth a try because I just went through some bunch of reviews and it's somehow disappointing, truly some of their third parties are scam
Exactly. Personally, I wouldn't recommend their swap service because better safe than sorry in case our funds are stuck due to 3rd pars provider issues.
So eXch.cx only requires the two swap address and the Api takecares of the rest with the fee??
Yes, it's working like that.
Swaps are really easy and straight forward. No KYC, no account required, no shenanigans.
eXch.cx is also active here on Bitcointalk,
more information is available in their ANN.
You'll also find all available coins in their ANN.