Percona Server 5.7 replication is slow than 5.6, huge delay

MySQL & MariaDB Percona Server for MySQL 5.7
1

We are plan to upgrade Percona Server 5.6 to 5.7 because of the replication delay problem during peak hour and hope 5.7 MTS will fixed the problem. We make a test at stating server, before the upgrade we can do about 6000 insert/s without delay. But after the upgrade we can only do 3000 inserts/s. The 5.7 version is 5.7.13-6-log. we only changed these parameters:

slave_parallel_type changed from database to LOGICAL_CLOCK
slave_parallel_workers changed from 2 to 8 // we only have 2 databaases so we use 2 in 5.6 for parallel replication
sync_binlog changed from 1 to 0 //with 1 it is even worth

Is there anything need to change?

Thanks