I use Standard 365 for everything, from small 3/4 pound cups to 45 pound planters. It throws great and is pretty forgiving for a porcelain. Yes, it must be quite thin to go translucent. The thicker a porcelain can be and still go translucent, the more prone it is to issues like slumping, warping and cracking.
I have seen translucent porcelain that uses EPK, a domestic kaolin. English Grolleg is not a necessity. It's more about formula and glassiness.