Power Combos Basic's

The damage of power combo explosions depends on the rank of the source and detonator power, not the stats of the power. So if you combine a rank 6 Pull with a rank 6 Throw, you will get maximum combo damage. Whether you use Throw or Warp to detonate doesn't really matter, except when that power has special upgrades to increase the damage of combos. Even if Warp, by default, does more damage than Throw on a regular impact, this does not affect how much damage is done on power combos - only the rank of the power matters.

This applies for the other combos as well. Using a rank 6 Incinerate to set up a fire combo and detonating with a rank 6 Throw will cause maximum damage. Using a rank 1 Incinerate with a rank 6 Throw does the same damage as using a rank 6 Incinerate followed by a rank 1 Throw, which is less than having max rank in both powers.

The power upgrades for increasing combo damage (ex: Warp rank 4 bottom choice) applies to both setting up and detonating the power, but only some powers can set up combos. So for Warp, that upgrade will increase the damage when setting up and when detonating. Throw doesn't set up combos so its combo upgrade only applies to detonating. These upgrades do stack, so if you have both the Warp and Throw upgrades, setting up with Warp and detonating with Throw will apply both bonuses.

All 4 combos (Biotic, Fire, Cryo, Electric) have different radius, damage, force, and other effects. The Fire combo, for example, does the most damage, while Cryo is fairly low damage but has the added benefit of freezing nearby enemies. Biotic and Electric are in the middle for damage, but are easier to do because the target doesn't have to die when detonated.

The combo damage is done after the normal power impact. So if you detonate with Warp, Warp will do its normal damage and then the combo damage is added.

Power bonuses from gear and passive powers (like +10% power damage) do not affect power combos; however, power combos do what we call "normalized" damage, meaning they scale with enemy health. So even on the hardest difficulty where enemies have more health, the power combos still do the same % damage to the enemy. 

This makes them scale really well with difficulty, which makes up for them not scaling in other ways like getting power upgrades from other sources.

Power combos do not cause other power combos. So if you create a biotic detonation near an enemy in Stasis, the detonation won't cause another power combo.

A power can only detonate a single combo every time it is cast. So if you have AoE Throw and you hit 2 targets both in a singularity, only one of them will get detonated.

Henchmen do the same amount of damage as the player when it comes to power combos, so it doesn't matter who set up or detonated the combo. The only thing that matters is what rank the powers were.