Insert into table select - Replication lag - Percona Server 5.6

I have two MySQL instances (Percona server 5.6.31) in Master-Slave replication setup.

I have set the below configuration:

1. ROW based replication is set.
2. Transaction Isolation is set to read-committed.

Today, there was a insert going on in my Master. It was in the format

INSERT INTO table1 SELECT * FROM table2

Table 2 has 200 million rows.

Though the number of insert records was only 5000 but the operation lasted for 30 mins. I observed replication lag during the insert operation.

I have load infile disabled due to security concerns. Hence I can't insert using that as well.

I went this article from Percona which says that this can be resolved if txn isolation is used as ROW and versions above 5.1 that this is resolved.

1. In what way I can make my slave to be in sync with Master in such conditions?
2. Why does the slave lag here?