I'm currently DMing with the Encumbrance variant, and both my players and I love to add some depth or realistic sense to almost every aspect in the game (that we are able perceive). But, as a matter of fact, we don't like to homebrew rules indiscriminately, so we try to play the rules as RAW as possible in the vast majority of cases.
So, here's our case: Our Human fighter (17 STR) wants to carry the unconscious body of our Half-Orc Warlock (242 lb). Starting from this, his max carrying capacity is 255 lb. (15 times his STR), therefore, he shouldn't have a problem carrying the body, so, he should have a penalty of -20 speed and disadvantage on ability checks, attack rolls, and saves that use STR, DEX or CON, but at least he should be able to carry the half-orc body.
We are fine at this point, but, does it count the weight of the carrying gear of both creatures in the total lifting weight?
For example, the Fighter is actually carrying 56 lb. of gear, and the half-orc warlock is carrying 10 lb. as well. Even adding the additional weight of the warlock gear, the fighter should be able to carry him (252 lb.) without getting the exceeding carrying capacity penalty, as the PHB on p.176 says; but if I need to add the fighter carrying gear weight as well, he should get the 5 speed drop penalty.
Push, Drag, or Lift.
You can push, drag or lift a weight in pounds up to twice your carrying capacity (or 30 times your Strength score). While pushing or dragging weight in excess of your carrying capacity, your speed drops to 5 feet.
So, how should I resolve this situation? And what is the real penalty that our fighter should suffer?