I often use this(笑) or www.

笑う, hm. In English, we sometimes say "lol" out loud. Could 笑 be said out loud as well, and if so, would that be pronounced わらう？

"w" is the initial word of "warau" (笑う）, so we use" www"

When I cried with laughter or I'm falling down, rolling on the floor laughing（爆笑）