Some torrent search/index sites and torrent trackers may be blocked, but torrent traffic itself is not blocked in China, at least on the domestic ISPs I've used. I can download a debian image over bittorrent, without VPN, without a problem. In fact, it can be faster than download directly over http, as the traffic has more potential routes.
Last I was there, Astrill seemed to be the way to go. But the situation evolves.