Import is very old code that is single threaded. AMA is all brand new and is multi-threaded allowing more cores to the transcode process. In most cases, AMA->transcode is at least twice as at fast as import. Also AMA’ing to clips in v7 give you far more control via source settings such as reframing a shot (frameflex” and ability to apply 1D and 3D LUTs.
For now, the background process is only for transcoding. I suspect we will see “save and render” in the background in future releases. Exporting would be nice as well.
Michael