Traansrate is reall a terminology for providing a different bitrate, and perhaps resolution, rendition f a live stream. It's still re-encoding the video stream and takes about the same CPU cycles as
the transcode process does.
There are some encoders out there, such as FMLE, that can provide more than one bitrate version of a stream (perhaps a high and low) before reaching Wowza. Wowza can then ingest those streams
and provide the various protocols as needed. This merely shifts the transcoding to the head, or source, end so you still need a system with sufficient power to run the encoder, but that can be a good laptop
or desktop PC. FFMPEG could also be used, but would have similar CPU requirements for the same process.