Controlling overdrive transmission

Changing 904/727 to A500/A518 I'm investigating the subtleties of controlling overdrive and lockup when gently accelerating on the freeway.

Both the PATC kit and the delay relays option drop overdrive and lockup together when the throttle is opened. I'm wondering if the TC lockup and OD are equally fragile and if it would make for a smoother drive if they were controlled independently - perhaps using vacuum for the lockup and throttle position switch for the overdrive.

Can anyone tell me what happens on a factory car with overdrive and lockup when the throttle is eased open when cruising at 60 to 70mph? how much does the pedal go down before LU and OD switch out? Do they go together? If not, which goes first and how much more pedal is required for the second change?