If the video was ripped and prepared as a scene release, it’ll download the specific subs for that release using the meta data (assuming they added it when released). If not, I haven’t ran into a single issue using Jellyfins Opensubtitle plugin to grab a generic subtitle file for the movie/show if there is no scene info. Its always lined up well.
Don’t really need a very powerful server to run Jellyfin. Most NAS hardware, or a Raspberry Pi 3+ handles it just fine. I ran it on a Raspi 3b for several years.
Jellyfins own “on the fly” subtitle writing works fine too…