So for stun-alching I think the difference is between injected vs mirror mode. Injected I was getting crazy xp rates and unrealistically high efficiency/timing while stun alching but in mirror mode even after messing around with response rate/fps the bot would stun/curse, click high alch, and then wait almost a full second before clicking my item. Selecting curse and attacking the NPC was normal and quick but it seems like the alching part in mirror mode is delayed.
Also, just regular high alching seems to be much slower in mirror mode as well, injected I was getting 65k+ xp per hour while in mirror mode I'm hovering around 55k. Just wanted to give a heads up if you wanted to look into it