I wrote about this before, my thoughts are:
If you are fighting a guy who is strung out on drugs, too drunk to feel it, or just plain batshit insane, the loss of 1 arm will probably NOT end the fight in and of itself.
Everyone else will most likely back down as they have just lost a limb, and if you took 1 you can certainly take another.
In my humble opinion, chokes should be move #1 as they incapacitate and don't leave any lingering damage. Second to that would be severe leglocks, because if you're going to do a sub that leaves lingering damage, might as well incapacitate and run the hell away.
No I don't fight, never have fought, this is pure theory. I don't have any reservations about using BJJ in a typical club night fight, I would say 90+% of all fights I've ever seen happen are sloppy boxing matches 1 on 1. I'm sure people get X on 1'd and lose all the time, I've just never seen it. If I were IN any of the 1 - 2 dozen fights I've seen break out, I'm pretty confident straight up BJJ would have won the day had either guy used it. Everyone has a puncher's chance standing, but once the fight hits the ground, it's sharks and guppies.