That would be a half halt Instead of constant tension on the lead you do little quick checks to keep the dog collected but not strung up20" collar ???? That seems very large. You don't want them to have a bunch of play in the collar. I would think a 16-18" would be fine.
You don't want to use a martingale type collar like the one you posted because it catches the hair. Ditto the one Kpoos posted. I'm surprised that a poodle person would give you one of these because I would think the coat would catch in that slide.
My handler uses the following show collars with a matching lead:
If Enzo is running, you need to 1. slow his gait back to a trot and 2. get him to carry himself.
Too many dogs pull/hang on their leads, poke their heads and necks and sort of skitter around the ring. This is the kiss of death in a Poodle who is supposed to have upright carriage and movement with suspension.
Some people simply string a Poodle up. This is where you hold a very tight and short leash and basically hold up the dog. Many dogs will fight this or they will gag in the ring. I saw one dog actually throw up. I think it is ugly and you will run across judges every now and then who will make you show a poodle on a loose lead.
I think a better method is what in horses we call a half halt. This check and release.... check and release method encourages a Poodle to collect himself up and move with good self carriage. I've seen Betty Brown use this method.