Other players are likely to use hardware accelerated decoding, while WATCHOUT uses software decoding. There are technical reasons to why WATCHOUT uses software decoding, related to all the functions WATCHOUT provides (which are not available in simple players).
Firstly, you might want to look at the frames used in encoding. Use only I frames and P frames - do not use B-frames. Most encoding tools default settings will use B-frames, so you may need to tweak your encoding settings. While hardware decoding seems to handle B frames well, they incur significant performance penalty in software decoding.
We would recommend learning how to use FFMPEG, as it is a very powerful encoding suite allowing you to tweak the preferences to a much higher degree than what you will find built into a lot of applications such as Adobe.
Follow this guide to get up and running: https://video.stackexchange.com/questions/20495/how-do-i-set-up-and-use-ffmpeg-in-windows
Here are some sample commands to use when encoding videos in h264 (25Mbit bitrate), mpeg2 (50Mbit bitrate) and HAP respecively:
ffmpeg.exe -i input.mp4 -c:v libx264 -preset slow -tune fastdecode -profile:v baseline -g 30 -bf 0 -b:v 25M -y output.mp4
ffmpeg.exe -i input.mp4 -c:v mpeg2video -g 30 -bf 0 -b:v 50M -minrate 50M -maxrate 50M -bufsize 50M y output.mpg
ffmpeg.exe -i input.mp4 -c:v hap -format hap_q -y output.mov
Files encoded this way should have excellent performance in WATCHOUT.