@Dan Smith watching your videos reminds me of why I don't offer remote bike fits. The potential for perspective error and insufficient frame rate are two concerns. That said, this an extremely interesting forum for discussing what we do observe, and a fantastic opportunity to learn and share knowledge. I mostly agree with @Gary Radford although I'll mention my observation relating to your left shoulder and leg in a bit. As for your right heel siting slightly inward compared to the left, the twist in your sock graphics makes we wonder how much is actual foot rotation versus visual confusion. I accept that there is likely to be some inward rotation of the heel as that would sit well with my observation about your left shoulder and leg. I'd also like to test Gary's observation regarding saddle height and pay particular attention to the effect on ankling and plantarflexion. I'm not concerned about the angle between torso and femur at the top of the pedal stroke, but I would be investigating what appears to be excessive bouncing. More evident in the left profile view to my eyes. The caveat being that I don't know how much force you are producing to be able to say whether that might be reasonable or not. It could indeed be a symptom of the saddle being too low. What I would like to see is a view from above your pelvis down onto the saddle to help assess any pelvic rotation both statically and when pedalling. And markers on the left and right iliac crests or other prominent landmarks to assess horizontal pelvic movement when viewed from behind and help differentiate that from gluteal contraction. The combo of black bibs and indoor lighting make it difficult on video. With regard to your left shoulder and leg, you exhibit exactly the same characteristics and symptoms as me. Hence my eyes being drawn to it. In the front and rear views your left shoulder clearly sits lower than the right. Your left knee tracks vertically, but appears to move slightly inside the imaginary line between hip and foot. Subject to potential perspective error of course as the camera is not directly in front of that leg. The knee tracking is more evident in the rear view to my eyes.

@Gordon Russell a few questions and I'll number them to make it easier to respond: 1. Does the gastroc pain occur off the bike or only while riding? 2. Does the gastroc pain occur with flat pedals or only with clipless pedals? 3. Is the gastroc pain more prominent at a particular phase of the pedal stroke? 4. What are the two types of bike that your friend rides? I assume there are two bikes or does he just change pedals? 5. Is there a difference in his stance width with flat pedals versus clipless? 6. Do your friend's knees move up and down in a vertical line above his feet or do his knees stay outboard of the imaginary line between hip and foot? Possibly more prominent around the top of the pedal stroke. 7. Does your friend feel pressure on the outside edge of one or both feet when clipped in? As if his feet want to be further apart, but that is resisted by the shoe. I have a head full of ideas, but without actually seeing your friend while pedalling it is a process of elimination.