Yes, only new connections will be balanced between the two nodes.
If the online node can support all the connection you can leave the connections on this node. Then when second node its online the new connections will be balanced.
Restart the application its a extreme action and its not necessary, thats why you are using a Rac to allow application to keep working normally.
I agree with J.A. Since the second node has just restarted, Oracle should detect that it has a lower usage and new connections will be directed to connect there. Eventually the connections should balance themselves out between the two nodes as old connections close from node 1, and new ones connect to node 2.
Remember that when you are using two node RAC configuration you always should make system (hardware) configuration so that your application can also run in one node without problems. Because if you get outage for one node then only node that is left should be keep up the work. And yes database LoadBalancing is only affecting in new connections.