Put the pack on loosely with buckles loosened. Shrug your shoulders up holding the wt of the load. Firmly cinch the hip belt which should ride a little high on your hips. If you loosen your shoulders at this pt the pack shouldn't fall down so much as it will fall away from your back and shoulders. Cinch the shoulder strap webbing to get the pack up and closer to your back. Neither of you should have a pack sagging pulling on your shoulders. Your loads don't look exceptionally heavy or bulky. It appears the soreness is related to pack use adjustments as much as might it being a poor pack torso length fit. Snap your sternum strap making a final adjustment to the shoulder strap webbing. Use load lifter strap if your pack has them but it doesn't look like your pack does where your BF's pack looks like he has them. Part of your shoulders being sore is the shoulder straps being too loose with the load too much pulling on your shoulders away from your shoulders and the load bouncing around...coupled with the shoulder straps falling off your shoulders because you're not using your sternum strap. Use your sternum strap high enough so that it's not pressing against your lungs and chest yet keeps the shoulder straps from falling off your shoulders. It shouldn't be so high to choke you either. This will help alleviate that shoulder soreness.
Both of you proceed at a nice personally suitable pace with a good awareness. Love both your smiles, sense of gratitude and positive energy. I wish I was doing some of the same trails to meet both of you.