Hello Alvaro,

Thank you for reaching out and I am happy to help!
1. All images converted with the webp converter are sent to a third-party server maintained by the W3 Total Cache team which reduces resource consumption and allows for a large number of conversions in environments where resources can be limited such as shared hosting. Images sent to the W3TC server for conversion are only held temporarily and no permanent information is kept on the server regarding the images.

WebP optimizations with the Image Service tool do not replace the original image file and all conversions can be reverted without any loss of data. The images are always served as webp when converted as we are using the rewrite capabilities of your server to serve the images as webp.

2. I am not sure if you are referring to Varnish integration in the W3TC or the Varnish servers. With the W3 Total Cache, you can connect top your Varnish server that needs to be previously configured, and perform a Purge if and when needed. For details about the Vrnish itself, you should reach out to your hosting provider.

3. You can check more details about how to Configure Bunny CDN with the W3 Total Cache in our article, and this being said, Please note that there is a difference when setting up CDN and FSD CDN

I hope this helps!
Thanks!