Configuration of server for 100 Users

[TheDreadPirate]

Having media files that don't have to be transcoded should be a priority. Transcoding is going to bog Jellyfin and your server down.  Like any high demand, high resource computer/server usage, having adequate memory, CPU and bandwidth is a start point.

I would add that even without transcoding, that many simultaneous users would pretty much require SSDs for the storage.  The IOPS and throughput of an HDD is not sufficient.  Even if in a RAID.