The Gemara says that romaine lettuce, chazeret, is preferable. Rava says chazeret is calles chasa because HaShem was chasa al yisrael, and R’ Shmuel ben Nahmani says “Va’Ymareru Et Chayeihem” alludes to the Mitzriyim like Maror to teach that just like Maror is initially soft and is hard in the end, also the Mitzriyim were initially soft and hard in the end. Lettuce is initially soft, and if left too long in the ground it becomes hard.
And regarding a hashash of gebrokts- the same daf says you are yotzei if the marror is wet (but not cooked, shelukim, or kavush). If they were worried about gebrokts, Hazal wouldn’t have stated you are yotzei with marror that’s wet.