If you stay clear of subtitles and any video codec that is not H.264/AVC, you should be able to use it for 1 transcoded stream at a time.
https://www.cpubenchmark.net/cpu.php?cpu=Intel+Core+i3-5005U+%40+2.00GHz&id=2484
Even if you buy a Plex Pass, you won’t be able to use other video codecs with hardware transcoding, as this is an old “Broadwell” chip:
See this thread Hardware Acceleration and Intel Atom X5-Z8350
