I do SEO for many WP based sites and have tested several other plugins. ShortPixel is by far the best in terms of feature and simplicity. All my clients (subaccounts) now use ShortPixel exclusively and they're very happy with it. A few feedback:
1) Advanced option to run on Cron (For site that have 5k++ images and having my computer/tab on for a few hours is hassle)
2) Define/Limit website domain name for subaccounts (to prevent key from being leaked by other people working on the same site) OR mask the key once entered.