That's not really a capacity topic but more about your experience. When people 'play out of turn' they upset the balance yes.. but as noted that can be solved by keeping people from getting out of turn. That problem is exaggerated the longer a meal is. But look at it the other way around.. assume people don't camp out and meals are not actually a long seated experience. Does mobile order make the place turn over more orders? No, the kitchen will still be the ultimate speed limit on customer throughput. Taking more orders than you can fill just creates a backlog.. guests not being able to be seated just clogs up the downhill side of things and causes negative sentiment.
Mobile order like many 'convenience' models only really is a benefit when no one else is using it. When it becomes the dominate way of doing something, those advantages tend to disappear.
Something like getting your order in faster because you're avoiding the trolog in front of your line is great.. but if 50 other people are doing it too you've lost that advantage.
Lines are useful as self-regulating. When the line gets long enough, human nature will cap how long the wait gets. Mobile order fails at that.. which is why when SWGE opened you ended up with the stupidity like lunch selling out at 9am and other absurdities.
Mobile ordering has benefits.. but like many things, the real total answer 'depends'. Order pickup works great for turning over hand overs quickly.. but you gotta throttle it, else you end up with the situation like 300 people trying to all stand around the same 10ft of counter space.