You want to search for BDMV for full disc images, or for remuxes which are uncompressed video and audio streams, if you want to get a sense for the size on disc. Typical Blu-ray images will be from 20-40ish GB.

It really depends on your hard drive space and your tolerance for compression. Two hours of decently compressed video is a few gigs, but if you want 10-bit HDR with 5.1 audio, then choose the 15 gig torrent.