The gloomy new champion Vex, has been out for a bit now, so this article will focus on her. I will quickly go through the meta of various regions, where she is played and in what roles.
Vex is mainly played in the MID lane with occasionally tried out as support. Now lets compare the pick rates and win rates of the main region solo queue. (Platinum+)
(displayed as pick rate% - win rate%)
So immediately we can see, it is a lot less popular in China than in the rest of the world. China played nearly 3 times less Vex than the rest of the regions. Most - at NA with the lowest win rate out of anyone.
Also something to note about builds. Most of the world agrees and goes with Electrocute keystone in the majority of games. Except Korea. They play Vex with Arcane Comet. Even though the numbers are very close, just a few percentages apart.
From the item side of things, it is hard to build something different on a full AP scaling champion. So every region has Ludens Tempest, Zhonyas, Deathcap items. Some people try Everfrost build too.