Hi Lauri, so both of those options actually do the exact same thing with the only difference being where the object origin gets created and what the new retopology object’s local orientation is.
The lag in RetopoFlow 3 is from displaying the low poly mesh on top of Blender. If you hide or separate out the areas that you’re not actively working on (like the face of a character when you’re working on the legs) then the lag should be kept to a minimum. I know that’s not super convenient, but that’s exactly why we’re overhauling everything with RetopoFlow 4.