after a bit of morning research:
YFTK = Shenzhen Yuanfei Tech Technology Co., Ltd.
Chinese name: 深圳市遠飛泰克科技有限公司
Date of Establishment: 2016-05-18
Can't fin much more about them... company in shenzen, 5 years old... and really no more info about them, and I even checked Chinese sites

Shenzhen Coppervape Technology Co., Ltd.

Coppervape... well they have a fb page, and unlike yftk's fb page it is actually not dead.... so If somebody need more info about them just need to ask, I am sure they happily answer...

Oh also they have a shitty unprofessional website... so trash it's worth to check out :D coppervape dot com... it is hilarious, looks like a middle-schooler's unfinished home project...

You sure ShenRay only resells Wejoy stuff? On their site they seemed like a genuine manufacturing company... For example Taifun GTR 25mm is listed on ShenRay's site, but on Wejoy they only have the 23mm... idk man...