Hello,
Yes, this will require two transcodes as you are arriving at 3 different streams:
1) 3000Kbps source stream
2) 500Kbps CDN stream (transcoded from source)
3) 200Kbps internal/local stream (transcoded from source or #2)
Transcoding #3 from #2 will reduce your CPU load, as there is less data being processed, but it will add additional latency to that 3rd stream. If latency is not a concern, i would choose to re-reencode #2 to arrive at #3.
When pushing to CDNs, i would suggest to push using the EMS pushstream command. The EMS has a much more robust implementation for RTMP (and RTSP as well).