go with OQL Query for the large amount of data transaction. https://marketplace.mendix.com/link/component/66876
Microflows are fine, but you should not do that in one action. It should perform better if you do that in batches. Maybe 1000 Objects in a microflow. This microflow can now be added to the task queue 50 times.
With this pattern, you can make sure that the database transactions are not becoming too big.