You can use both firm or silken tofu. If you use silken tofu, make sure you stir extra gently because it is easy to break.
Most ready-made chili bean sauces use a small amount of wheat, so even though this dish looks fairly innocent; it’s NOT gluten-free. For a gluten-free version, replace the chili bean sauce with gluten-free chili oil.
Regular soy sauce is made with fermented wheat. Use gluten-free soy sauce if you are gluten intolerant.