What type of data/configuration/events are continuously synchronized between the 2 TSIM servers when installed in application HA mode. 

All operational data is synchronized.  This includes the following.

1. Events
2. Performance Data (trends) collected by PATROL agents and other sources.
3. All configuration in the DB (discovered monitor types, monitor instances, users, monitor policies, etc.)
4. Event Policy and event cell data class content configurations stored in the event cell.

What is not synchronized 
 
Configuration settings stored in text files.  This involves content like the following:

1. Heap size settings, timeouts, event retention periods, etc.  These are primarily stored in .conf files.
2. Event Cell Knowledge Base customizations including rules (.mrl files), data class definitions (.baroc files), event class definitions (.baroc files), collectors (.mrl files), record definitions (.baroc files) and .load files.  These are all under the …pw/server/etc/<cell name>/kb directories. 

Basically, all operational data is synchronized while custom code/configuration is not synchronized.  So if/when you create and apply custom code and/or edit any text configuration files for tuning performance/scalability, then those settings need to be manually applied to both the primary and secondary instances of the TSIM server(s).