> The term normally used is 'manhwa'.

I don't know about English usage, but in Korean these are different concepts. "Manhwa" (만화, maan-hwaa) means "comics", usually in print. The Korean word for an online comic is "webtoon" (웹툰, ooeb-toon). This is the usage, for example, on Naver: NAVER 웹툰 is the title of https://comic.naver.com. Of course the webtoons borrow a lot from manhwa style, but one buys/rents manhwa at a store and reads webtoons on the subway. So they are different concepts and "webtoon" is the proper Korean term for this phenomenon.