re : AK flop CR

if you get called after CR flop it's basically the same spot as getting called when u C-bet OOP in a 3-bet pot and have air on the turn

it all comes down to history with villain, your image, etc etc etc

as for the 27s (w back door draw) vs A7 mid pair top-kicker, I'm more inclined to bet A7 for value whereas I prefer calling with backdoor draws

it ll be almost impossible to put us on a back door draw if we pick one up, lead the turn and hit the river (lots of other options like calling flop and CR turn if we pick up a back door draw)

other thing is we get called much less often by worse when we bet 2nd pair meh kicker and have no idea where we are at , OOP on the turn and are forced quite often to give up or turn our hand into a bluff-catcher

i d prefer leading this flop with complete air than with 2nd pair meh kicker