In the absence of any other responses I'll give you what I believe to be the correct answers for the 737NG with a health warning that I don't go on the 737 conversion course until January but I do have 36 hours 737 sim time.
The basic rule is that whenever the buttons are lit they are de-selectable.
Auto Throttle Switch - is de-selectable
Speed – De-selectable and results in throttle arm
N1 – De-selectable and results in throttle arm
Lateral Nav – De-selectable and results in HDG SEL
Vertical Nav – De-selectable and results in ALT HLD(plus THR ARM I think)
Flight Level Change - De-selectable and results in CWS PITCH (and a throttle mode? N1 I’d guess)
Heading Hold – De-selectable and results in CWS ROLL
Vertical Speed – De-selectable and results in CWS PITCH and N1 modes.
Altitude Hold – De-selectable and results in CWS PITCH
Localiser - Not de-selectable, another mode must be selected.
Approach. - Not de-selectable, another mode must be selected.
As I said I am no expert and I could wrong so perhaps a 737 pilot confirm or deny the above.
SW