When doing sysbench tests against standalone mysqld vs. single node Galera instance vs. two node cluster performance differs between MySQL and MariaDB setups.
With both MySQL and MariaDB standaline non-Galera nodes show best transactions per second throughput when not having to do any commit time fsync, as expected. Meaning that things are fast with innodb_flush_at_trx_commit != 1 and log_bin disabled or sync_binlog=OFF
A single node MySQL Galera setup shows almost the same numbers, is fast in the same config combinations.
A MariaDB Galera 10.x cluster, with 0 <= x <= 2 at least, shows a slightly different behavior though. Here only the combination "innodb_flush_at_trx_commit != 1, log_bin enabled, sync_binlog=OFF" is almost as fast as a standalone non-galera-enabled instance with the same "no fsync" settings. When disabling log_bin transactions per second go down quite a bit, to similar values as if innodb_flush_at_trx_commit was actually enabled.
I first suspected that group_commit might play a role, but Binlog_commits and Binlog_group_commits counters were always showing equal values in SHOW STATUS output, so this can be ruled out.
When running sysbench against a 2 node cluster performance differences were not as massive as in the single node setup, which was to be expected, but still visible.
So while turning off innodb_flush_at_trx_commit; and sync_binlog if log_bin is enabled, is usually considered safe in a cluster (if the hardware setup is redundant enough, e.g. simultaneous power failure on all nodes can be ruled out), and to improve performance/throughput a little bit, it turns out that with MariaDB the performance improvement is only visible if binlog writing is enabled, which is at least counter-intuitive.