The THR-22 does not support TiVo To Go. TTG is the feature of transferring the show to your computer and burning a DVD. Some older TiVos even had the DVD burner built in. Your only option is to connect the THR-22 to a DVD recorder or video capture card and archive in real time.
As far as external hard drive goes, yes the THR-22 uses the eSATA for an external drive. Keep in mind an external is meant as a replacement of the built in drive. If you use the eSATA you will not have easy access to the recordings made on the internal drive. It is not meant for archiving like Dish does it. It is used for more recording capacity with DirecTv recievers.
As far as external hard drive goes, yes the THR-22 uses the eSATA for an external drive. Keep in mind an external is meant as a replacement of the built in drive. If you use the eSATA you will not have easy access to the recordings made on the internal drive. It is not meant for archiving like Dish does it. It is used for more recording capacity with DirecTv recievers.