The Standard Group is the most flexible group. It is commonly used as a bi-directional sync between your PLCs and databases. In addition to this, it can also be used to push data in either direction. This means the Standard Group can be used to store historical data, add to/update existing tables, and create recipe management tools.
The Historical Group is the most straightforward and simplest to use. It will take OPC data and store it as history in a database.
The Block Group is used to efficiently store large amounts of data in blocks or chunks of similar data in the database. This is very useful if you have many devices with the same Tags in them.
It is possible to configure your Standard Transaction Group to be able to get information from one OPC data point to another. This is useful in the event that you have Tags coming from one PLC and you need the Tag information to be sent to another PLC on your plant floor.