Our general recommendation for a HA server based on a 4 node design: High Availability
The configuration of this done in the exact same model as the user-based licensing; the installers and Server software does not change under different licensing model, just the license keys and the considerations you need to have. In a core based model, the limitation on the deployment is based on the core count available across the nodes in the distributed configuration. In general, if each node has 8 cores and there are 4 nodes, the licensing would require 32 cores (8 nodes x 4 cores) to support the architecture. There are processes that are counted towards licensing and others that are not; it is possible to configure nodes with a combination of processes that would not be counted towards licensing. In the configuration described in the article, the primary and back up primary would not count against licensing; the workers do count against core licensing, and if each node represents 8 cores - the license key needs to be able to support at least 16 cores (2 workers x 8 cores). This article might help to understand what processes are counted in licensing in core licensing: Tableau Server Processes
As for the GCP environment, keep in mind that the virtualization doubles the core count :Not All Cores Recognized by Tableau Server | Tableau Software
We typically recommend that each node should have at least 8 cores, and this would translate that you should not use instances with less than 16vCPUs in GCP for each node.
Lastly this might be good reference on what to consider and how to build out a distributed environment: Distributed and High Availability Tableau Server Installations