The two strategies aren't meshing well in my understanding. Consider: combat starts and Improved Grab for a limb hold is applied to all enemies.

At this point, there are two options.
(a) Convert one limb hold to a grapple, and apply savage grapple (possibly repeatedly). This does substantial damage, although it's reduced depending on the limbs holding enemy creatures. This requires 8 class levels.
(b) Convert one limb hold to a grapple, pin, add some damage, apply chokeout (Fierce Grappler 5), and then stranglehold (Black Blood Cultist 5) for the kill. This requires 10 class levels.
Both of these are good combos, but the synergy of (a) with (b) is limited since (b) works well enough without (a).

Method (b) is more limited, since it requires opponents vulnerable to critical hits and to strangulation.