What kind of paper is commonly used for hard-pen calligraphy in calligraphy competitions? And a soft pen?

In general calligraphy competitions, the specifications of paper will be explained. If there is no explanation, there is no requirement for paper specifications in this competition.

Besides, I don't know if you mean the writing brush by soft pen. If so, raw Xuan paper is generally required in the brush calligraphy competition, because it absorbs ink and has strong artistic effect. The size of the specifications generally varies with the requirements of the competition.