what is the best digital output format for miniDV tapes
h.264.

For DV the default settings will probably be fine:

ffmpeg -i 'dvgrab-001.dv' output.mp4


If the footage is interlaced (the ffprobe says it isn't, but if you see combing artefacts then use this):

ffmpeg -i 'dvgrab-001.dv' -vf yadif output.mp4


The original video is anamorphic NTSC 4:3, meaning that it's stretched slightly out when played back, this should be fine with the TV, but if not you can re-sample to make square pixels:

ffmpeg -i 'dvgrab-001.dv' -vf scale=728:540,setsar=1:1 output.mp4


If the video is supposed to be 16:9 but is playing back squashed you can set the Display Aspect Ratio thus:

ffmpeg -i 'dvgrab-001.dv' -vf setdar=16:9 output.mp4


Or resample for square pixels thus:

ffmpeg -i 'dvgrab-001.dv' -vf scale=960:540,setsar=1:1 output.mp4