Now those are just the basics and everything can be either modified or substituted. For Vegan or Vegetarian options just sub out those unwanted items with nuts, tofu or other options of low carb, high healthy fats and proteins. For dressing options, oil and vinegar are for the most part the healthiest option. Stick to the Braggs apple cider vinegar for all of those great health benefits. For the oil portion you can switch off between 3 choices. Olive oil, avocado oil, and MCT oil. The first 2 taste very similar and offer a pleasant, savory taste to the salad. MCT oil is the most nutritious, but is mostly void of any flavor.
As far as dressings off the shelf go you’ve also got a fair amount of options there. Caesar, blue cheese and ranch are very low carb most the time. As always, check the label! Companies will add sugar into everything, so you never know. Most of the dressings marketed as low calorie will be almost exclusively carbs, so try to stay away from those.