Duke Blues, for the fastest video encoding, if you have an Nvidia GPU, try software that uses it more for the encoding process, e.g., NVEnc or CudaCoder. For Intel GPUs you want to use software that utilizes Intel's Quick Sync. The disadvantage is that GPU-based video encoding will be [slightly] lower quality than software based. Depending on the selected output format, the ffmpeg code libraries used by most converters OTOH offer very limited hardware acceleration -- it's not the ffmpeg devs' fault, but the encoders themselves that it uses. Note that if you do use something like CudaCoder you will have to handle DRM beforehand.

That said, most video players will resize / enlarge video on the fly, often doing a better job than resampling during encoding. Reencoding video also loses quality -- DVD video is purposely lower quality to discourage reencoding. If you can live with the video file sizes, converting DVD video to mpg2 files without reencoding preserves original quality, and takes almost no time, but not all players work with mpg2 nowadays -- VLC does. To improve the appearance of upscaled subs you can use something like SubtitleEdit to OCR them to an .srt file, which most players can handle.