A heavy paper is a necessary condition to paint with watercolors. If the paper is too light, it will hardly absorb the water. You will wait very long until it dries, the paper will crinkle, etc.
I use some 300g/mē (140lb) watercolor paper, either ARCHES, SENNELIER, FABRIANO or WHATMAN (although this last one is more difficult to tackle). Other brands are worth consideration. The main point is paper heaviness.
Conversely, roughness (rough, not or hot pressed) is not so important and depends mainly of the final precision of the work. No rule here. Try and adopt the one you prefer.
A convenient mean to paint outside may be to take a paperblock. But beware paperblock quality is not always good (light or second quality papers).
Hint: Get quality big sheets to cut the size you need (jesus size for instance: 56 × 76 cm, 22" × 30") or even rolls. It's cheaper and you cut it exactly the size you want. Sometimes that's the only way to proceed, for instance for panoramas.
