We often put our own spin on recipes.  That is what makes them our own. It is often said that recipes are like road maps.  You should use them the first few times then feel free to improvise and take a detour.  At least that is what we always tell our students. How ever, classics are classics for a reason.  You will find different versions of the Salade Nicoise even in Nice. Different families will have their on version and depending on availability of ingredients some may use one vegetable rather than another.  According to Jacques Médecin in his book Cuisine Niçoise there are certain rules that MUST be followed, one is you either use tinned oil packed tuna or anchovies, not both. I must admit that I have found chefs in Nice that do use both and the locals do not seem to mind. The second rule of thumb is no cooked vegetables are to be added. There go the green beans and potatoes so often include.  Boiled eggs are fine. In all honesty I use both in my Salade Saumonée de Nicoise, but then again I used salmon, not tuna AND anchovies. Because Nice has only been been part of France since 1860 much Nicoise cooking is simple and not overly saucy.  In the classic salad no vinaigrette is used (especially one with Dijon type mustard), just a good fruity olive oil with fresh herbs and a sprinkle of sea salt and pepper. You can use regular lettuce, but most common is a mesclun.  Mesclun always has a mixture of five (5) different leaves and  may include mâche, lettuce, chicory, arugula, escarole and radicchio or even baby spinach, purslane and dandelion.