Some (not all) of your questions may be answered by the linked article near the top of the submitted article, which goes into more detail about how much is lost

Some (not all) of your questions may be answered by the linked article near the top of the submitted article, which goes into more detail about how much is lost quantizing to 1 bit (and 1 byte): https://huggingface.co/blog/embedding-quantization https://huggingface.co/blog/embedding-quantization