Clickbait remover uses YouTube's auto generated ones, which while are seemingly random, are not. They use some algorithm to target faces in exaggerated expressions.
DeArrwow uses actually random ones (and then a user can submit specific timestamps if there is a better one). It's noticeable better on many channels imo
Yeah, especially for some creators like veritasium where they play "musical thumbnails" and change it every few days for about a week or so. It's so annoying because I keep thinking it's a different video.