Yup. If the sd card doesnt have enough space for everything, you could attach an m.2 hat to it as well. https://www.raspberrypi.com/news/using-m-2-hat-with-raspberry-pi-5/
Basically, jellyfin on the pi, with the wifi setup as an access point, and whatever amount of storage you need. The pi requires 5v/5a, so you’ll probably run into issues running off the car usb power, but a cheap 30amp hour battery should run it for 6-10 hours if my napkin math is right.
I have a pretty solid average of 2-3 terabytes of download a month. My upload is between 4 and 10 terabytes a month.
I stream a lot of movies, youtube, etc. So does my roommate. I once had a sales rep in a different apartment say over the phone that I wouldn’t need to worry about the data caps. I laughed and hung up. I’d rather have slower speeds with no cap than higher speeds with a cap. there’s no point to having all that data if you spend the whole month worrying about hitting the data cap.