To check things, you can always run etcd itself:
nix run .#etcd
and the client:
nix run .#etcdctl -- --help
To run mergeable etcd run:
nix run .#mergeable-etcd
mergeable etcd uses the same client as etcd above.
To run dismerge run:
nix run .#dismerge
dismerge has its own client, to run:
nix run .#dismerge-client -- --help
To build clusters the datastores follow the same arguments as etcd, so please follow their guidance (without TLS): https://etcd.io/docs/v3.5/op-guide/clustering/