I don't know what CentOS 9 is like, I've never tested or installed it.
Centos 7 is quite stable, but over time it will fall behind, it only receives security updates.
To be able to install version 9 of Red Hat, Rocky Linux, CentOS, AlmaLinux, Oracle Linux, etc. ( Red Hat based OS ) you can use v8 templates.
For example, I use Rocky Linux 8 templates for VMs with Rocky Linux 9, but I also used Red Hat 8 template and it's ok.