Yes. It is possible to define the specific search peers you need in each search head.
Each indexer and search head has its own license configuration. If you are using a license server all the indexers and search heads has to point to the same license server. If you have 2 license servers, you could have a set of indexers and search heads pointing to one license server and the other set pointing to the other license server.
More information about license server:
I have seen that as well as the docs on search pools, so thanks for helping me understand which one I want. When adding a peer, what license file is used and does replicating the data consume license volume?