According to me, one the best sketchbook for watercolor is the Etchr cold pressed sketchbook.

Not really possible to use it for pen and ink, but for watercolor, this heavy paper is the best.

I love the look of the sketch, and the paper is very forgiving. I can go back to the clouds with no risk of dirty blooms.

You can compare it with the 3 tests I did on the other sketchbooks from my previous posts. On smooth paper, the colors are more vivid, but I find it more difficult to create soft edges and mix colors on paper.