Hi Sedar,
In my experience w/ Rives BFK I have found that every different version of BFK for example 150gsm, 285gsm and 300gsm behaves deferentially, it is a printmaking paper as opposed to a watercolour paper in regards to size additives AND texture. I have not tried the 300gsm BFK but I have had just great results with the previous mentioned. In addition I have printed on the front and back of the same weight and found the front to have a slight sheen as compared to the back which produce a better dMax and image appreciation.