Hello ,
Thank you for posting in the community your question regarding the M1 and Path Tracer. You can reference the current information regarding the status of the technology in this article: https://twinmotionhelp.epicgames.com/s/article/Path-Tracer-Requirements
Regarding dual GPU support I recommend you make this suggestion on the road-map:
https://portal.productboard.com/7pu88c9kpmqtzt8hwg6arujh/tabs/4-under-consideration
Some Mac users have used rendering services for the Path Tracer such as iRender
https://irendering.net/twinmotion-cloud-rendering-service/
Kind regards,
Vincent B.