No. Inexpensive tiles are thin because they are typically mass produced by a machine that allows the clay to be compressed into a dense but thinner tile.
All tiles are not the same thickness and most handmade tile lines are thicker than inexpensive tile lines.
No. Surface glaze irregularities like pin-holes, occasional small specks, glaze build-up, glazed-over nicks and chips are not defects. The hand of the ceramic artist is evident in the irregularities and variation that is inherent in a handmade and hand glazed tile and part of their charm.
No. However, to maintain color purity when glazing over red clay, an initial layer called an "engobe" is applied. Using white clay eliminates this step and may help keep production costs down.
No. NEVER mix white, off-white or neutral glazes from different tile lines. Factories use different bisque and glaze recipes and over the expanse of a wall or floor, they can look very different from one another. Even if the samples look close there is too much variation when installed next to each other and this problem is amplified with hand painted glazes. A sample cannot tell the whole story.