Some brown rice flours are grittier than others...the bulk ones are usually coarser. I just bought Arrowhead Mills in bulk, and it seems to be a little finer than the usual bulk one we get.
We don't use potato starch, and keep tapioca to a minimum, as they are nutritionally void (same with sweet rice flour and white rice flour, both of which I use sparingly). My favorite flours are teff and sorghum. We also use buckwheat and millet, and sometimes grind almonds to a flour. I like them because they are higher in fiber and protein rather than just starchy carbohydrates.
Also, I like whole grain baked items, so I may be less sensitive to flour choice than you are. What are you trying to make? If you use the more healthful flours, it's like as if you used whole wheat flour--much better for you, but not that refined-food texture.