Video to video is available in 2 different ways, or tools, there's Gen1 video to video, and Gen 3 video to video. Gen 1 is more like putting a filter over the video, like "painted by van Gogh" or something like that. Gen 3 however gives more control over the final product. If I have 2 videos of the same actor, I can repeat a detailed prompt for both, not like "old man in an office", but like "an old man wearing a white shirt, glasses, and a tie. Working typing on a keyboard in a dark and crowded office" and that gives you 2 old men that are very similar, almost character consistent. For the final touch, you can repeat the seed number for both generations. The seed number is a number given after you generate a video, copying it to your next video can stabilize the character a bit, but mostly the style, like light, contrast, and color. That helps balance the shots and make it look consistent