I would agree with you about the partnership between the bread and the rest of the sandwich. My experience is that most are usually dominated by the bread as well. Usually, Hamburgers or Clubs are exceptions but it’s not a guarantee.
As for your preference to Helmann’s over Calve…I agree, but have you tried Zaanse?

Pasta Tricolore does a great aubergine, red pesto and provolone sandwich. My only criticism of Amsterdamian Sandwich culture is the generous sized bread often overpowers the contents of the sandwich, and I feel a sandwich should be a partnership, not a competition.

I thought the Sal Meijer sandwich was quite overrated. From what I’d read in Frommers and other blogs, the Sal Meijer Hot Partrami (Salt Beef) sandwich was supposed to be the find of Amsterdam but I found it quite an ordinary sandwich.

Also I know I will probably spark some transatlantic foodie riot when I suggest that in my humble view, Calve is an inferior mayonnaise to Helman’s.