PNG to WebP
Your images never leave this device
WebP is the format to use when you want a PNG’s transparency without a PNG’s file size. It supports a full alpha channel like PNG does, but compresses like a JPG, so a transparent graphic that was 800 KB routinely lands around 150 KB.
How to convert PNG to WebP
The reason to bother is page speed. Images are the bulk of what most pages weigh, and cutting them by three quarters shows up directly in Largest Contentful Paint. Every browser released since 2020 supports WebP, so the compatibility argument that used to justify PNG has largely expired — the remaining reason to keep a PNG is when you need genuinely lossless output, such as a source file you will edit again.
Questions
Yes, a full 8-bit alpha channel, exactly like PNG. This is the main reason to choose it over JPG.