Galera Cluster Mariadb Slave replication from cluster, graceful restart and gcache

Hi all,
My environment : Galera Cluster Mariadb with 3 nodes (MariaDB-server-10.1.38 , Centos 7) , production databases .
I attempt to do "MariaDB Replication between MariaDB Galera Cluster and MariaDB Server" , make another server to become slave of this cluster , I read following instructions :
https://mariadb.com/kb/en/library/u...mariadb-galera-cluster-configuring-mariadb-r/
https://www.linuxbabe.com/mariadb/master-slave-replication-galera-cluster

What I concern : I have to apply new configuration (wsrep_gtid_mode, wsrep_gtid_domain_id, server-id, log_slave_updates, log-bin, log-bin-index, gtid_domain_id) into all cluster nodes and restart cluster gracefully.
How to do it ?
1. Rolling restart all nodes in cluster (one by one)
2. Shutdown and start all nodes in cluster one at a time (in order , shutdown n3 , n2 , n1 then start n1 with galera_new_cluster , then start n2 , n3)

If I have to do "2" , how to avoid SST when start n2 and n3 ? I know I should shutdown 3 nodes very quickly and the interval between them is short but just in case.
I read about gcache.size , gcache.page_size , gcache.keep_pages_size at https://mariadb.com/kb/en/library/wsrep_provider_options/ but I'm still confused about them.
My current (3 nodes) wsrep_provider_options : gcache.keep_pages_size = 0; gcache.page_size = 128M; gcache.recover = no; gcache.size = 128M
Should I change them to : gcache.keep_pages_size = 5G; gcache.page_size = 5G; gcache.recover = yes; gcache.size = 5G ?
I want to change gcache option so it is easier for me to add new node into cluster in future. Can I change gcache option in configuration file then do rolling restart all nodes in cluster ?
Please give me some advices , thank you very much.