For the second video, "Hair rigidification.mp4" I find no serious problems with the english, it is easy to understand. The only part that may be confusing is when it is mentioned "tie the hair" which I am not sure what it means, perhaps to link the hair together? The verb "tie" is not clear in its meaning.

Both videos are definitely helpful, I also appreciate seeing the difference with by extension and by neighbourhood on the hair simulation (although I still do not understand what is the exact difference between the two methods, but I know that is explained in another video you made which has not yet been given subtitles).