How can I Playback video files with no stop?
Unless you are willing to edit the videos together in one long video. I would use VLC, or load them all into iTunes (if the videos are iTunes compatible) and make a playlist to playback your videos.

With VLC you you should see very little dead time between videos, but you might get some jumping on the screen if they are of different resolutions. With iTunes it can be hit or miss depending on the format of the videos.

Here's the VLC playlist setup instructions: https://wiki.videolan.org/Documentation:Playlist/

You could do what you want with QuickTime, but it's rather tricky, and not as full proof as it was with QuickTime 7, or as easy as it is with VLC.

There's also the Elmedia Player, MPlayerX (which is based on open source), and 5KPlayer if you are looking for an alternatives to VLC or iTunes. I have used the Elmedia Player before when I needed to have Flash videos play in the mix. But I don't know if I would go with the 5KPlayer (even though it does supposedly have AirPlay support). It's from a Chines company that doesn't seem to be fully Apple Certified from what I can tell, so I'm not sure I would trust them.

I should also note that you will want the videos on a FAST SSD drive that's internal to your system, or connected over a fast connector. Otherwise part of the delay you will see between videos will be based on the load speed of the videos from whatever drive they are on.

I hope this helps.