Again, I think HTTP is better than RTMP for multi-bitrate streaming. There are other good reasons to use RTMP (security, cuepoints, familiarity with certain player), but just in terms of best streaming, HTTP is probably better.
Wirecast is a good encoder that works with Wowza, however it will not work as the source of several multi-bitrate streams for any type of multi-bitrate streaming, because the streams are not key frame aligned…
Wirecast will work as the source for Wowza Transcoder to do every kind of multi-bitrate streaming. The Transcoder ensures key frame alignment.
FMLE (read the EULA) will work as source of several multi-bitrate streams to do every kind of multi-bitrate streaming without using Wowza Transcoder. The problem is EULA restrictions, and in some cases uplink bandwidth. I.e., it is easier to send one stream to the Wowza Transcoder than to produce each bitrate version with the encoder and stream all to Wowza over the network.
I recommend the Wowza 3 Transcoder.