The Divx/Xvid codec inside the hardware chips of standalone dvd players are not very stable. Some will play back, some won't. Same applies with subtitling. It also depends on the file size, file properties and the filename.
How to pick the right torrent is impossible to tell. A torrent is just like a url, it hosts some data. I have no idea which are good and which are not, because it depends on what files you want.
You can forget about HDTV, unless you actually have a HD-supported television