Clustering and Domain Management are orthogonal. You can can have a cluster of EAP servers that are created and managed by a domain controller, or managed by some other means (common configs in multiple VMs). The performance of the cluster is not affected by the management choice.
Basically, you question is not only about cluster but also differences between standalone and domain mode.
So, here is answer for first question :
1. "advantage/disadvantage of standalone and domain servers cluster"
==> There are no differences of cluster because they are using same infinispan embedded library but only difference is how to configure it.
2. differences between standalone and domain mode.
==> Mainly, the points that you already know is right :
In domain one of the servers is management server and deployment is done centrally
Until EAP5, it was not possible to control each eap instance from central, which mean you need to configure each EAP instance. This could cause miss-configuration because it is human job.
From EAP6, you can use EAP like other WAS(weblogic, websphere). Other WAS products have this kind of admin console and node agent(which is similar to HC). Through this console, they can handle all configurations/deployment/life-cycle manament(start/restart/stop/..) Moreover, domain mode has server-group term. With server-group, you can deploy 1 application to many instance currently.
I believe main difference is how to control eap instances : central management or relative management