Recommended output settings for output to WebP with max quality?

[Kon]

I saw a recommendation online about using XnConvert, so far this looks exactly what I'm looking for.

My question is this: I'm looking to convert png's and jpg's to webp's and in the settings I selected lossless, but there is also compression method (defaulted to 4), filter strength (defaulted to 60) and filter sharpness (defaults at 0). I'm not sure what the min/max values are and if someone can give me a rundown of what these dials do exactly and in regards to converting to webp that would be fantastic.

Thanks!

[Tapio]

a) The filter settings don't seem to work, I created a bug report
b) viewtopic.php?f=79&t=42367