Forgot to answer your second question.
No-pull harnesses are aversive, as they are designed to tighten as the dog pulls forward. A front d-ring harness redirects/repositions without tightening, which means you can focus on rewarding the desired heel/loose lead position. (You never use the front d-ring on it’s own, which is why you need to use either two leads or a double ended lead.)
Opinions vary on head-collars. I personally don’t like them, a lot of dogs shut down in them and others spend half their time trying to get them off, rubbing etc. I have seen many dogs escape from them as well. That said, they can work for some dogs, if properly used. If you go this route, take some time to look up how to teach your dog to accept one and the correct way to use them.
Imho, a well fitted, comfortable harness with both front and back d-rings are the best option for non-aversive lead training/loose-lead-walking, but again, it’s important to take the time to introduce the harness to your dog in a positive/rewarding way before you start using it. Kikopup and Chirag Patel have videos on YouTube on how to do this.
Also lots of work at home on making walking alongside you the most rewarding position, with or without a lead.