Planet 4 is built on top of Wordpress, so it's important to keep an eye on what's coming in future releases. To avoid any surprises we use a variable in base repository composer file to set the Wordpress version for all instances. When a new release comes out, we first check its Changelog for any breaking change before we bump that version variable for Planet 4.
If we need to test a different version (eg. when a new release comes out) we can override that global variable for a specific instance. To do so we just need to add a similar section to NRO repository composer-local.json file. We can also override for just one environment by just adding that section to the environment's file (eg. development.json).