Incus is sort of like GCP's own resource management software, though GCP does a lot more than what Incus does. So you'd often be using Incus like a self-hosted alternative to GCP.
Meanwhile, running Incus inside GCP VM(s) should be possible, though I haven't tried it and can't confirm it. Incus can manage system containers - containers that behave like VMs running full distros, except for the kernel.
But keep in mind that Incus is more like docker than docker-compose. You will need a different tool to provision and configure all those containers over Incus's API (docker-compose does this for application containers over the docker API). As mentioned before, that could be Terraform/OpenTofu, cloud-init and Ansible. Or you could even write a script to do it over the API. I have done this using Python.
Meanwhile, running Incus inside GCP VM(s) should be possible, though I haven't tried it and can't confirm it. Incus can manage system containers - containers that behave like VMs running full distros, except for the kernel.
But keep in mind that Incus is more like docker than docker-compose. You will need a different tool to provision and configure all those containers over Incus's API (docker-compose does this for application containers over the docker API). As mentioned before, that could be Terraform/OpenTofu, cloud-init and Ansible. Or you could even write a script to do it over the API. I have done this using Python.