So would RFTs be better suited for autocrossing than road racing?RFTs definitely have stiffer sidewalls. It's what makes them RFTs. And it is commonly accepted wisdom that more flexible sidewalls give you better conformance to and traction with the road, at the expense of lateral load transfer (AKA "Transient Steering Response"). So RFTs should give you faster steering response but lower road holding ability compared to a non-RFT, all other things being equal (i.e., tire sizes and rubber compounds).
Drag racers use tires with tall sidewalls so that the sidewall can flex as much as possible since that leads to the greatest amount of traction. But you don't want to have to make any sharp turns with those kinds of tires...