To be honest you'd be best bringing this into and iMovie or Final Cut Pro Project with 16:9 then change the resolution to 720p.
Once you've done that, 'Export for Apple Devices' and choose 720p for your footage this would be the best option.
If you scale your DV footage up to 1080p or 4K it will reduce the quality quite a bit as it won't upscale very well.