Thank you for the review! I am glad that you use the extension and it helps you.

The extension does indeed fully block videos, reducing YouTube data usage. To verify, you can check the Firefox Web Developer Tools. Live videos are the only exception (as it is mentioned in the extension's description). The impact includes a decrease in CPU, memory, and a noticeable decrease in GPU usage (almost 0% usage), which directly affects power consumption. However, keep in mind that if you want lower CPU usage, you have to disable the "Always visible progress bar" option.

Hope this clarifies. Have a great year!