I'm currently trying out RPR under macOS to make use of my RX 5700 XT graphics card.
I noticed, that using Blenders in built smoke simulation the rendering inside viewport render is crazy slow (for me 50 seconds per frame) compared with the cycles renderer (approx 5 seconds). While RPR renders the viewport my Mac Pro 2013 becomes unusable (besides cursor moving no interacting of the system - feels like a complete freeze).
Are there currently known limitations? Has anyone else discovered this?
One thing I noticed is when switching back from Cycles to RPR the frame seems to render quite fast (3 seconds). As soon as I jump to another frame in the timeline the above described happens.