Having used Ergo levers since the mid 1990s and many different ft ders with them I understand that the detent steps, shifting response and chain rub can be a fine line sometimes. One thing I've done is to not use very narrow ft der cages. the other is to set the cable tension so that the lever settles into that last detent (of ft der travel) completely but no more travel can be had. This is done after setting the cage arrangement WRT the large ring and high gear combo.
But I have a very good skill/technique when shifting the front and almost never drop a chain or can't get the chain to shift. I know that this is not what many people experience or can do. (and the trend to eliminate frt shifting altogether is the result of so many riders not being able to grasp and learn how to shift the front well).
Back in the day with friction levers, symmetrical ring teeth, straight side plated chains, not sculpted cage plates and flexible frt ders we would tweak cages all the time. These days I see FAR less need and it's a rare set up that needs it. lastly I'll mention that when front indexing was being brought out (by Shimano) a little piece of instructional paper was included in the new bike packet (although not always made it's way to the rider
) which diagramed the ring/cog combos where chain rub was to be expected.
Lastly I'll say that if the system can be biased somewhat to not rub is certain combos, although at the cost of other combos being worse rub prone. Andy