Hi
Please go thro' below link explains you about load balancing with WCCP and multiple WAE
http://www.cisco.com/en/US/docs/app_ntwk_services/waas/waas/v4019/configuration/guide/traffic.html#wp1041807
Also, about unicast and multicat deployment the only difference is that On each WAE you need to configure multiple unicast router addresses in the WCCP router list, one for each router in the service group for unicast whereas for multicast, you just need to specify multicast group-address.
I hope this anwers your query