Need to fetch all events of all users under the same admin using single access token

Using a Dropbox Business API app with the "Team Member File Access" permission sounds like the right way to do this. 

To get non-file events, you can use the /1/team/log/get_events endpoint, as you mentioned.

To get file events, you will need to use the user-specific methods. In the Java SDK, using the asMember method to operate on a specific member is the right way.

There isn't a single way to get that for all members of a team though, so you'll need to iterate through and perform on each member individually. We'll consider this a feature request though.

For server-side apps, using webhooks is the best way to get notified of file changes quickly. For client-side apps, you can using longpolling.

As you mentioned though, the API v2 Java SDK is still considered beta, so we don't recommend using it in production quite yet.