Anecdotally, but hands on, I have a minisforum with a Celeron J4125 and 8 gigs of RAM and I've had no issues with transcoding on Plex or Jellyfin for the past 2 years. Both are running on docker with hardware passthrough, though I almost exclusively used Plex. This includes hosting a watch together for which my local device could direct play the file, but the remote party had to transcode and Plex pulling subtitles via OpenSubs on the fly. Subtitles specifically have never given me any great issue, except when they weren't available altogether. I was living in Germany until recently and without fail, my bottleneck was always my Internet connection (Crappy 5G internet, but my only other option was 6 meg vDSL). Power draw of that server was negligible and it has twice the TDP of the N100. Despite the lower power draw of the N100, it will soundly beat my J4125 on any benchmark or hardware data point. Additionaly, it has newer encode hardware for h.264/5 and more audio codecs. I mention that last bit because I have seen the Celeron occasionally struggle with audio, which results in forcing a partial transcode for all parties. All that being said, I do take some care in ensuring my media is all in the most compatible formats for the devices I'm serving (Mostly Roku and Apple TV), but that's just some time in Handbrake and trolling forums for what other users have found to work well.
All that being said, both the n100 and i5-9500T are fine choices for relatively low power servers. I chose my celeron for power concerns and have never regretted it. The only thing I would say you should consider is expansion. The i5, in addition to generally being the beefier processor, will be capable of handling more memory should you want to expand that down the road. Those EliteDesk style PCs, in my experience, will typically only take a single stick of memory, but they can go full tilt on a 32 or 64 gig stick. I have a SFF PC on standby for Hex that can take 2 sticks, so ymmv. For those reading this wondering if they goofed by getting a n100 instead of an older i5, I would say you have nothing to worry about, the nice thing about this category of home server is there are very few wrong answers, just caveats that may be worth considering. A far cry from my early days of tinkering where the best I could get was a Pentium 3 with 128 megs of RAM. It's a good time to be an enthusiast.
