I am using Audit log module for Drupal 8.5. But it looks the audits are very limited - i.e it audits only user updates and node updates. Not for creating templates, changing configurations, changing themes , creating pages, views etc. Since this site will be audited , I believe I might need more than this.
Any help on how to achieve this?
IMO the Message module would be a possible solution to answer this question. Using this module, you can create your own custom "Events logging" (to register things that happened in a site).
About Message types: think of them as equivalent to Content types, whereas you create messages (instead of nodes) of a specific Message type (instead of Content type).
A great sample of this can be found in Commerce Kickstart, which uses the Commerce Message module, to create such "Events logging". In that case in the format of an Order History, as shown in this screenprint (from this module's project page).
The Message module is an amazing module, it is fully entity based, which implies that it perfectly (out of the box) integrates with modules such as Views, etc.
Though there is not a lot of documentation about it (which is what makes it a hidden gem ...). A possible way to get started with it, and to get an idea of the kind of things it can be used for, is to have a look at the answers to:
Tutorials:
