I think if I ever do actually CTB it will likely be by hanging - but if I had access to other things it definitely wouldn't be and I think the same goes for most people.
Most accessible methods of CTB have low success rates. However, hanging (at least when done right) is very lethal. The most common reasons people fail are poor anchor point, ligature breakage, or SI. Every story I've heard of hanging has to do with inadequate set-up or SI, you never hear of it just not working like how it sometimes does with people taking SN or pills or something. If you can overcome SI (or do full suspension and completely remove this issue) and you ensure that your rope, knot, and anchor are all tested to bear excess of your weight, there's very little that could stop it. Pretty much the only thing is someone finding you. If I hang myself I plan to do it on old hiking trails which have been closed that are gated off from the public and have to be climbed over - won't be home so my family wouldn't see me, and I think being found and saved within time there is very low-chance as to even get in there you have to climb a locked fence and trespass. I plan to do it at 3 AM or something too so visibility would be low and chances are no one would even see me off to the side of the trail hanging from a tree.
If I could, my method of choice would definitely be overdose. I work in healthcare and I can tell you that 90% of people who overdose have no recollection of it following resuscitation. You die without even knowing it. The issue with this though is that street drugs are not predictable in their concentration and dosage. Pharmaceutical drugs are pretty much impossible to get. Otherwise I would consider firearms, but I have a known history of mental illness and suicidality, and in Canada you need references to state that you are not suicidal to be granted a firearms license. A middle ground for me might be injecting myself with medications and then waiting for them to kick in so I drop onto the rope and hang without experiencing the associated pain/discomfort.
I remember a few months ago I saw a post where someone had linked to an erotic video of a woman being hanged and then lifted up - in that instance it didn't seem painful or unpleasant. If you practice hanging it doesn't necessarily have to be painful (or at least so I've been told by some people on this site), but things can always go wrong at the last second. The rope can slip into the wrong position, maybe closing your trachea and suffocating you instead of pushing on your carotid arteries and causing you to black out. As long as suicide is self-administered, there will always be these issues. Performing a "procedure" on yourself which necessitates you to lose consciousness will never be 100% reliable. Even lucid surgeons sometimes mess up during procedures, so people trying to kill themselves will too.
On the Dying With Dignity Canada website, they discuss the medications that are used in MAID (medical assistance in dying) provisions. Midazolam to sedate you and reduce anxiety, Propofol to put you into a comatose state, and then rocuronium to stop you from breathing. Any anxiety you have would be prior to administration of the first medication and would quickly disappear. This would be my preferred method. I think in general if suicide was medically supported and there was less animosity and stigma surrounding it, it would be looked down upon far less. Hopefully one day MAID will be legalized for anyone with any reason for not wanting to live - as long as they can demonstrate maturity and serious intent surrounding the decision. Healthcare workers I know who have been/are involved in this process have told me that a MAID death is the least traumatic type of death. It is controlled and peaceful, people get a chance to say their goodbyes and die (at least relatively) comfortably and not in pain. I think eventually in the future maybe people will realize this and pretty much everyone will die from MAID - apart from accidental deaths (at least assuming the anti-suicide fanaticism doesn't continue past the near future).
