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. It also let’s us do things like make sure the random thumbnail is not in a sponsor using SponsorBlock data
(I made DeArrow)
Creator of theq extension here, that is an optional permissions (may ask). It never asks to access to all sites, it only optionally let’s you add support for additional sites such as different Invidious instances. These are arbitrary domains, so it needs permission to ask for any arbitrary website.
Support for invidious is not actually done yet, so right now, it never asks for permission for any new sites anyway
The client side data is used to store your submissions to always show your preferred title, even if there is another submission on the server. You can disable this option in the settings
It replaces it with the much more pleasing artwork from the actual video. Someone has gone through and picked nice frames for many of those videos.