I found edging is good mental discipline training. But it didn't physically change anything for me- just gave some practice in the old mental game.

No climax vs ultimate climax is a mixed bag for me. I generally choose to not climax and save the built up steam for a partner. But I wouldn't say it necessarily increases my stamina.

Exercise and yoga seem to help because when I'm stronger I'm exerting less energy doing the body weight workout of sex.

Also do kegels for exercising your PC muscles- that helps for sure.

You don't have to even practice meditation but I find it helps. Just being aware of your breathing is huge. As you approach climax your breathing patterns get more intense. If you slow your breathing it can be a game changer, and can reset the clock by relaxing you and pulling you back from the edge.