I just checked on my *arr stack. Sonarr and Radarr idle at 157MB and 159MB of memory and approximately no CPU. Jellyfin currently idles at 330MB. I'm not sure where you got this impression from. I grant these tools are complicated and have somewhat clumsy UX, but they aren't especially heavy to run and are not fragile.
OP, point your :robot: at https://github.com/subdavis/selfhosted/blob/main/docker-comp... and ask for an explanation. It's a single compose file that illustrates how the *arrs, transmission, and jellyfin all work together. I'm sure you can set it up :)