If configuring WFE server with
Distributed Cache, during installation would this server have to be installed as a custom role?
Distributed Cache service can be added later after installing a WFE server role.
During the installation process you have to select the "Front-end with Distributed Cache" role and complete the configuration. Post configuration, you can apply changes to your DC if any( changing max memory, service account etc).
You should be at least on November 2017 CU level as this role introduced in that cu.
No, just install it as DC+FE. You can add further DC+FEs later.