That is true, Coolify supports magic variables to make your life easier by automatically creating values like passwords and URLs, but you are not forced to use them, it is just there to make your life easier, some improvements to the naming and docs for the magic vars are planned.
For docker-compose, I had to create a specific one for Coolify because it goes and does its own magic.
Tried Dokploy(similar service), better UI but lacking in docs.
In the right hands, these products could be so much better.