Welcome to the forums @hbonnaf
80MB is very large for a background video. How long is it, what is the bitrate, and size? Short and small is the general “rules” for such things (IMHO.)
Netlify Large Media states
Netlify Large Media is not suitable for streaming audio or video files. However, storing these assets for download should work well.
so that is out.
Files over ~5mb are not (as I understand) sent out across the CDN and are instead streamed from the origin server. This will impact performance on a file that large.
This would entirely depend on the amount of traffic the site is likely to generate. 80MB (0.08GB) goes into 100GB a lot. But by the time all other content is taken into account, it could go over this.
As for how bandwidth is calculated, check out What does actually count in bandwidth? - #2 by luke
Services such as Cloudinary, or ImageKit, both offer image/video hosting and provide transforms, allowing different sizes for different devices. This is possibly the best option.