We'll need tracking (if I understand correctly, we need previous values). When calling SaveChanges often, how do you handle rollback in case something fails?

Either wrap everything into a transaction or just call SaveChangesAsync only once. The exact behaviour depends on the database here, under the hood this uses database transactions.

You can use .NoTracking() and an SQL query for bulk changes ( and minor changes). Eg. Updating one column.

Works faster than with .Tracking. The SQL script runs in your transaction, so rollback runs as usual.

The i%20==0 condition with .SaveChanges() is used with .Tracking(), yes.