It all depends on how you process things.
Plex on the Linux server side w/ 12700K has a couple of options for processing the files post recording. CPU / iGPU / dGPU.
On my laptop I further convert things from ts to mp4 using MCEBuddy that monitors the folders I set and automatically converts them. It has options to use the same as the server. I set it to use the GTX1650 and it takes a couple of minutes per file depending on the file. It seems to combine CPU / GPU processing on some files while using GPY only on others. I think it has something to do with the codecs it detects when it scans the files.
Before some tweaks in configurations 1.5-3X processing times were what I was seeing as well. Laptop is using a 9750H but, with those higher processing times IIRC the "NUC" I was using had a 5500U CPU in it and didn't really perform all that well for this sort of thing. I also had a NAS that worked to an extent for acting as a server 24/7 but the processor was under powered if it had to transcode anything.
So, here's the server post-processing a show with ffmpeg to scan for / remove commercials in a hour long recording and it completed the task in ~90 seconds. If I ran it through MCE to kill commercials it would take considerably longer. They both use the same underlying software to process things but, different methods.