Combine potatoes and 1 Tablespoon of salt in a large pot. Fill with water to completely cover.
Bring the water to a boil and then lower heat and simmer until potatoes are tender (test them for doneness by piercing them with a knife - they should be easily pierced by not fall apart), 8 to 12 minutes.
Drain the potatoes into a colander. Place the potatoes over the empty pot (off the heat) and cover with a clean kitchen towel. Let them steam and cool for 15 minutes while preparing the dressing. (Letting the potatoes steam prevents them from being water-logged.)
Whisk together apple cider vinegar, lemon juice, mustard, sugar, salt, and shallots. Slowly add in olive oil while whisking.
When potatoes have cooled, pour dressing slowly over top, gently folding it into the potatoes until they are well coated. (You may not need all of the dressing right away to complete coat the potatoes, but they may absorb more as they sit. If you have some dressing leftover, save it and you can stir some more into the potatoes right before serving.)
Let potato salad rest in the fridge for at least 2 and up to 24 hours for the flavors to blend.
Just before serving, fold in fresh herbs. Taste and season with some more salt, if needed.
Serve cool or at room temperature.