Why Write IOPS,Write throughput,Queue depth decreased on AWS/RDS after changing innodb_flush_log_at_trx_commit and sync_binlog?
Both of those changes improved throughput, but decreased robustness.

innodb_flush_log_at_trx_commit=1 says to flush stuff to disk at every COMMIT, thereby making your database fully crash-proof.  =2 risks one second's worth of COMMITs.

If you have the binlog turned on, sync_binlog=1 says to flush to disk at every COMMIT.  =0 allows delaying (buffering) the writes.  This variable is somewhat important if you have Slaves and/or do incremental backups.