I use both plex and jellyfin and my files are on a nas. Previously truenas but now synology. I just mount my collection over smb to my Intel nuc with quick sync so that Plex/jellyfin can provide me and my friends a slick UI as well as transcoding (can store stuff in hevc, flac, 5.1 or 7.1 dts hd ma and not worry about codec support on each device), a nice web player with subtitles /audio track selection, and nice apps on every device to access the collection.
But yeah NAS and jellyfin aren’t mutually exclusive, many people use them together.
A dht crawler is inherently an intensive service to run, magnetico used sqlite and would take 10 minutes just to load the splash page that includes the total count of discovered torrents.