Plex only supports NVENC for GPU acceleration, and only on Windows.
As far as I can tell, all NVidia GPUs between the 1050 and the Titan XP have NVENC support, and a user-submittedAmount benchmark suggests their per-thread performance is pretty much identical across devices, with the difference mainly being how many NVENC processors each card has.
From that benchmark, it seems your 1050 Ti should handle transcoding fine. Try downloading a demo (e.g. Big Buck Bunny) and test it out.