It should be possible to compare the different alternatives. All 3 can either work directly (by establishing clubs) or by enabling a
♣/
♥-squeeze. For simplicity I assume RHO will always play low with the ace (except with A, AT or if he got the queen) and that LHO would always play the 6 if possible (even if having the 4, not considering probabilities, restricted choice theory or signalling tendencies). I also assume Frances does not find any clues written in the ceiling and end up playing the king in her latest scenario, since this keeps the squeeze chances if LHO got QTx.
1. Playing the 7:
Wins in 4 cases (LHO got AQT64, AQT6, QT64 and QT6), but no additional squeeze chances.
2. Playing the J:
Wins directly in 4 cases (AQT64, AQT6, AQ6 and AQ64). Additional squeeze possibilities in 3 cases (QT64, QT6, Q64).
3. Playing the K:
Wins directly in 1 case (AT64). If you plan to just play a small club next if the king wins and no Q falls (to rectify the count for a squeeze) a squeeze is possible in 3 cases (AT6, A64, A6).
This simplified analysis indicates that playing the J is best and that the 7 is better than the K. But playing on Vugraph one may consider that playing the king is the fanciest play
John