I am planning to move to Elementary OS and was wondering if there is a kind of compatibility chart. I'm planning to buy an ASUS UX390UA, but I would like to have everything working properly. Like sound, Wifi, bluetooth, keyboard, ...
There is an Ubuntu hardware compatibility list (https://certification.ubuntu.com/desktop/) though no Asus machines are in the list. That doesn't mean they aren't compatible by any means. It just means they haven't been tested by Ubuntu (elementary OS's base).
Personally I've seen Dell machines work best with linux. I've never had any compatibility issues.
I did some digging for you, and couldn't find anything in the official Ubuntu Hardware Compatibility list. However, I own an Asus E403S which works fine with elementary OS - I know it's older than the one you're looking at, but it's similar.
Also, there is an Ubuntu Forums post here that shows that there are at least a few minor issues surrounding that particular laptop. Asus makes nice laptops, and the hardware is fairly standard, so I say go for it.