Should config via cli rather than gui?

I agree with Aswin on management, configuration, and troubleshooting.
Regarding HA, I would say you must configure changes on the active chassis to see the impact of the change. If you make a change on the standby chassis, you cannot confirm whether it works fine or not.

Also, we have two options for configuration sync: Automatic and Manual. If you use the Manual option, it provides a safer way to roll back the configuration. Make the change on the active chassis first; if everything works well, you can sync the configuration. Otherwise, you can sync the configuration from the standby chassis to the active one.

Hi Herman2024 

You can use the CLI to configure management IP addresses. To log in to the CLI, you need to connect to the system using a management console or console server, and then log in using an account with admin access.

You can use the Configuration utility to update or upgrade BIG-IP HA systems. 

For HA clusters, you should make configuration changes on the active peer and wait for the changes to sync to the other peer before making any additional configuration changes

FOr me i am using GUI for all administrative works in LTM,GTM,AFM,ASM and APM. CLI using for troubleshooting purposes (logs, captures, connections status). Also management interface(ssh,httpd) related changes aswell performing via CLI

BR
Aswin