I used Litespeed plugin in a Wordpress website (Litespeed Server hosting) and the Webp images where always bigger in size comparing to .jpg's.This module enables different types of optimization, it even modifies the .htaccess of your site.
The problem mentioned is that the module delivers the images in .webp with a .jpg ending, this is to make some browsers or CDNs like Cloudflare compatible.
About the images being big is a bug even with the .webp itself, I recommend leaving the compression at 80%, after converting all the images, clear all the cache.