I did some calculations assuming that Bernal has an exceptional power to weight ratio (~7) for a 20 min effort but only average aerodynamics and Evenepoel has exceptional aerodynamics and a very high power to weight ratio (~6,5) but lower than Bernal. Using my estimates it seems that up to a slope of 4-5 degrees, Evenepoel has an advantage. I also tried to estimate Evenepoel vs a peloton (where the chasers have an aerodynamic advantage) and it looks like Evenepoel may already have advantage from a 2-3 degrees slope and upwards (unless they are all TT guys with reasonable climbing abilities). These are just rough estimates and there are many variables at play (weather, road conditions, energy left in the tank, mental abilities etc). Still, it may explain why Evenepoel can put minutes in to a chasing group, in particular in a hilly stage. It also means that if Bernal has indeed a better power to weight ratio, going with him to a final long and steep climb might not be the best strategy unless you can drain his energy prior to the climb.