And how to choose right weight of paper in sketchbook?

Before you make this decision it’s crucial to understand the difference between cotton and cellulose paper. Many people that have had experience with cellulose paper would consider the 200gsm cellulose as unsuitable for their needs. The thing is, it's not only the paperweight and the thickness that differs. Most of all, it's about the quality of paper and its hardness. To put it simply, 200gsm cellulose is not the same as 200gsm cotton and you would be able to feel that difference.