Thinking more about post below I realized just like everything else in Jiu-Jitsu, fundamentally sound Guard Passing strategies are based on distance:
Elbows to hips is a great strategy to employ when an opponent opens their closed guard because their hips are still tight to our body, but they haven’t got their feet to our hips yet to create distance. Here the bottom player is ripe for under/over passing combinations.
Along these lines, watch and feel where the bottom player’s hips are, and defend and attack accordingly. Here Henrique from Marcelo Garcia’s academy employs the above principle of under/over passing from a granby guard recovery (hips in tight to body, but no connection):
If hips are further away I’m going to fill that space with my legs or go around depending on the bottom players energy and pressure. In fact, thinking about this more it’s pretty much a longer distance version of previously discussed tight under/over passing.