Mostly the defense thing. Does it apply while card is unpicked on the field, or do I have to pick it to take effect? Can it be used by the enemy? I didn't get to test those much because combined with the rng it would take quite a few tests and paying attention to the hp.
The similar thing was with understanding the limit. It's hard to have the understanding because I have to track the points, pull off a large enough combo and then notice the differences. It's hard being empirical with that underlaying mechanic.