What I love about your comment is that you are using more or less the same methods that were around when the RPi3 came out.
I didn’t consider weighing the storage penalty vs the cost of processor upgrades when keeping an SD or 720p version of files around. I know some people run two instances of radarr/sonarr/jellyfin for this reason. Like many, my connection is asymmetric, meaning the best I can probably serve is 1080p over WAN at maximum luck, or a few simultaneous streams mixed between 720p and 480p.
Example: Asteroid City is 18.5 GiB in 4k and 3.5 GiB in Web 720p, a roughly 5x’s file size difference. If we estimate SSD cost is ~$50/TB, 5TB of 4k content costs an extra $50 to keep 720p around for WAN streaming.
That to me justifies not upgrading processing, using instead an RPi3 for low power storage maxxing, and eating the cost in file duplication. I simply won’t be able to get on-the-fly hardware transcoding capability anywhere close to this price point.
Ngl, I was pretty bummed about the realities the previous commenters enlightened me to in this post I’m very grateful to their wisdom. But, you have given me so much new hope!