BIG-IQ any value if you don't use it for config changes?

So BIG-IQ is a management platform, for managing devices, deploying configs, viewing statistics etc. You can do all of those things with other methods - Ansible, Splunk etc.

Iirc it will soon be the case that you can just have the license manager as a standalone which you can run in a container or suchlike and it will be separate from BIG-IQ.

Having said that, if you have a lot of devices then BIG-IQ can be a very useful platform and licenses are pretty cheap so it can be worth deploying it anyway even if you only use it for backups etc