The most useful tools of Site Guru :

1. Unlimited audits : no credits, no limitation
2. A unique timeline : Discover changes and what Google changed

Basic stuff :

PageSpeed : identify slow pages
Indexability : Find blocked pages and the reason why (robots, noindex)
Broken links : they send a bad signal to Google.
Google Search consone : I was able for one website, but not for the other. Not yet reported to the staff.
Google Analytics : not used beacause not GDRP. Any project for Matomo ?

The limitation of 500 pages is ok for my websites. More pages would be good when a site grow. Anyway, It's a good deal because you don't need credits to run audits. It's very useful to follow corrections you made step by step.