You thought your questions were "quick" but they were actually complicated to explain, because you mixed up a lot of things.

Why do you want to "consolidate"? Applying for subsequent Citi cards is easier with lower total credit limits at Citi, not higher ones. So just "cancel", don't "consolidate".

Cancelling a World card will restart your 18-month clock.

Cancelling a World Elite card appears to have no effect on the 18-month clock for now. (We cannot tell what effect it may have if/when the W->WE "loophole" ends. And we cannot tell if/when the W->WE "loophole" might end.)

If all you have is World Elite cards, you can cancel them any time you want. But I'm confused, because you said you have 2 World Elite cards, but then you talk about 3-4 cards. So it that forecasting the future, or do you have one or more World cards that were never updated to World Elite?

And before you ask: We have no concrete information on conversions. It's quite likely that a conversion from a World AA card to a no-annual-fee card would be treated as a "close" of the World AA card and start a new 18 month clock. But everyone who's considered that has read about this possibility, and has either not converted, or not attempted to apply for another AA Plat MC after that, or simply not reported on what they did after that and what the results were. So we're left with just worries, but not facts, about conversions of World cards.

No. It doesn't matter whether it's your first or twentieth card.

The 18 month rule looks backwards, not forwards, for opens or closes of the same type of card. The 18 month rule ignores (opens and closes of) cards that became World Elite cards. (We call that the "W->WE loophole".)

The 18 month rule means that you cannot get a bonus for a new card if you closed any Plat MC World card (that isn't World Elite by then) within the past 18 months, or if you opened any Plat MC World card that hasn't been converted to World Elite yet.

So that's why I asked right above if you have any cards open which never got updated to World Elite, because unfortunately if you cancel those you'll restart your 18 month clock.