Backpacker
I think you've just proven "our" point, so next time pay attention
. No - the brace position isn't the same for every aircraft ( rear seating vs forward seating ) and the airline's vary ( feet forward vs feet back).
Equipment isn't the same - you claim life jackets are the same - guess what - they are not - some have nice clips at the side to do the tapes up ( EZE) others are "tie in a double knot at the side". Two tabs to inflate - not always - sometimes one.....
Slide rafts:don't have complete stats but they were used on the Kai Tak 747 about a decade back and there was also a 707 that floated quiet happily on Lake Vic a while back, plus a RAF Nimrod ditching..there are no doubt others.