According to Final Fantasy XVI director, the game's performance mode will always target 60 FPS, but will be better optimized during combat
"director Hiroshi Takai commented on the performance swings seen in footage captured in the game's performance mode, saying that this display mode will always target 60 frames per second, but may not hold the target framerate during exploration, depending on particular circumstances."
Probably a deal breaker for me not locking to 60. Should have used DRS. Will likely wait for the port to get more stable performance.