This ^^...
but since boomingblade directly states that the melee attack that is required is part of an action you need two actions in order to do two melee attack on two creatures
...
It’s the kind of ruling I would expect to see on Jeremy Crawford’s Twitter, rather than the kind of ruling I think is an intuitive interpretation of the text.
One uses the “Cast a spell Action” to use the Cantrip, not the “Attack Action”, the weapon attack portion of the cantrip is essentially a complex somatic component.
As I mentioned earlier, Booming Blade does say that you make an attack with the weapon used as the material component as part of the action used to cast it. One could argue that Twinning it doesn’t actually constitute another use of the Cast a Spell action, and therefore doesn’t provide you another opportunity to make an attack as part of that action, it only lets you designate a second target to be affected by the “if you hit it with the attack...” portion of the spell. I think such a ruling would be founded on an overly-technical reading of a spell that is written in natural language, but it’s the kind of ruling I would expect Crawford to give on Twitter.
As for Quickened Spell, yeah, I don’t see any reason that wouldn’t work with BB.
As part of the action used to cast this spell, you must make melee attacks with a weapon against two creatures within the spell’s range, otherwise the spell fails. On a hit, each target suffers the attack’s normal effects, and it becomes sheathed in booming energy until the start of your next turn.
* That's not meant to be rude. I understand that the effect of Twinning Booming Blade feels unusual. But the arguments against it really don't stand up to scrutiny.
Twinned Spell said:When you cast a spell that targets only one creature and doesn’t have a range of self, you can spend a number of sorcery points equal to the spell’s level to target a second creature in range with the same spell (1 sorcery point if the spell is a cantrip).
People are over thinking this.
Booming Blade is a single target, non-self spell. Therefore you can Twin it.
What does the Booming Blade spell say?
You target a creature with a melee attack because you "must make a melee attack". If it hits, it deals weapon damage + additional thundering effects.
It doesn't say you take the Attack Action. It says as part of the spell that you make a melee attack.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.