Historically, none of the manufacturers of Chinese origin seemed that interested in selling healthy or tested products. To me it seemed they did little if any testing and used consumers as Guinea pigs. Most tanks were made of polycarbonate plastic, which would crack or melt if certain flavors (primarily cinnamon or citrus flavors) were used. Due to consumer demand, they eventually began to use glass instead of plastic. Today virtually all tanks are made of stainless steel and pyrex glass -- thanks to consumer demand.
Aspire came out with a revolutionary new coil head design a couple of years ago with their Nautilus Mini, but it used what they said was ceramic wicks (actually it was fiberglass, which crumbled easily and theoretically could be inhaled inadvertantly). Soon after introduction Aspire made the wicks from organic cotton.
Most innovations in vape gear are still pretty much "hit or miss", IMHO. I still think manufacturer "research and development" leaves much to be desired. I never purchased a new product, at least not the first edition of that product.
Some tanks that I recommend today are the Aspire Nautilus and Uwell Crown 1 tank. Both have been out for a couple of years; they are popular and proven.