Claim: There are  2 or 3 subgroups (GT3, GT4, and GT Open) in cars with Grand Touring label, but Touring Cars, which are designed for racing competition and motorsports are categorized base on their calculated engine capacity (TC1 - TC4).
Evidence: A grand tourer (GT) is a type of sports car that is designed for high speed and long-distance driving, due to a combination of performance and luxury attributes.