Difficult to answer.
The implementation of the ejb-client side is different to previous versions.
You should have a look here for examples.
If you use the JBoss specific API there are many posibilities.
The simple JNDI wrapper with the jboss-ejb-client.properties file can have 1....n different servers. where are the same, different or clustered applications deployed.
The EJB-client decide which real Bean will be executed depend on the name (ejb:EAR/JAR/distinctName/Bean!Interface).
Notice that the identifier is the name, so the same ear deployed on two servers might be loadbalanced nevertheless whether they are in a cluster or not)
If you add one server of a cluster to your client environment other member of the same cluster are added automaticaly (as in AS4/5/6).
Regarding your second question.
YES here are many with n-tier experience but it depends on what you are looking for You have to be a bit more precise