It’s always good to use the latest stable version of your major branch: Nextcloud server changelog
The enterprise version should be the same Nextcloud as the free one. But you get support. Some extended support you can even have stand-by support during upgrades in case something goes wrong they can immediately help you (rather large setups). But I don’t know how support is included in each support plan.
For logging there is also the audit log, I didn’t use it but perhaps worth looking at it:
You can combine a lot of information out of the nextcloud and webserver log, in case you want a quick and dirty solution.