Converting movies to run on NAS through PLEX




I have the “MY CLOUD EXPERT SERIES EX2 ULTRA” setup with Plex server installed in it. I have different kinds of pictures and videos stored there. I can view the pictures fine but not all videos would run in my TV through PLEX. I have all kind of videos (captured with different devices, some downloaded from the internet and other received from friends).

Googling further, I understood that it is because some videos need increased processing power which my WD NAS lack. Then it occurred to me if that is the problem then surely if I converted the videos using a software video converter to a format that these NAS devices are capable to render then that should do the trick.

I have not tried this yet but wanted to ask your thoughts on it:
1. Will this work? If yes then what FORMAT should I convert videos files to?
2. Does it more (or also) depend on the size of the file (ratio of quality and size) in which case surely there must be a converter to tackle it?
3. Are there any kinds of checks I should examine on the video files to know for a fact that it will run before loading it on the NAS (and testing it out on PLEX installed in my TV)

Any recommendations of freeware to achieve the above?

Please note that this discussion is about running videos on NAS rather than a laptop or PC.