verb agreement - How to determine the number of the noun phrase 'a world of + plural noun'?

a (or the) world of

is defined in Oxford as follows:

A very great deal of.

‘there's a world of difference between being alone and being lonely’

‘a bit of country air will do her the world of good’

I think the world of should be treated differently, so I'd like to focus on a world of.

Although the Oxford Dictionary says a world of means 'a very great deal of' and the phrase should be singular in that meaning, I've seen a world of followed by a plural noun. And when it's followed by a plural noun, I think it often means 'a great number of'.

The problem is, there is conflicting evidence as to whether a world of followed by a plural noun is singular or plural:

• And with the collapse of those ''walls'', a world of opportunities is opening before us.
  (SADCC at Ten, Address to the Tenth Anniversary Summit, Gaborone, Botswana. 24 August 1990. Published in The Missing Headlines: Selected Speeches, by Emeka Anyaoku)




• You've not yet developed notions of what you can and can't do (or what you should or shouldn't have done), and a world of opportunities is opening before you. (Confined Minds, by Raychelle Meyers, p. 25)




• A world of opportunities are out there for you. (The Strength of a Woman: Transformed for Greater Impact, by Claudia L. Roach)

Since 'a world of' here means 'a lot of', I'd think the plural treatment is more frequent, but the opposite seems to be the case. There seem to be more instances of the singular treatment.

So should 'a world of opportunities' be treated as singular?

How about this case?

This morning saw Jay-Z release his surprise new album ‘4:44‘ across all streaming services except Spotify – and a world of fans take note of the freestyle rap by his daughter Blue Ivy Carter. Check out the best reactions and the lyrics below. ("Fans react to Blue Ivy’s freestyle rap on Jay-Z’s ‘4:44’", by Andrew Trendell, NME Music News)

Here, too, 'a world of fans' I think means 'a lot of fans', but is followed by a plural form 'take'.
Do you think this is incorrect? Or should it be treated differently?
I for one think the plural treatment is correct, because it's the individual fans who take note, not the world itself.

EDIT

This question is not solved by an earlier question, "Is “an ocean of flowers” singular or plural?", where only two answers are provided and no answer is selected.

Moreover, the answer with most votes (2 votes) in that question seems to approve the plural treatment of 'an ocean of flowers', whereas my research about 'a world of opportunities' suggests that the singular treatment is more often than the plural treatment.

Most importantly, the earlier question and answers do not address cases where "an ocean of" is followed by a plural noun denoting people, which is raised as an important point in this question.

Answer

I haven't seen specific guidance on this, but I wanted to make an answer post to address something I think was missed in the list of examples in your question.

And with the collapse of those ''walls'', a world of opportunities is opening before us.

Here, it's not necessarily the case that "a world of opportunities" is just being used as a synonymous expression for "a lot of opportunities". The noun world in English can be used metaphorically to talk about a environment or ecosystem: access to a new
"world of opportunities" isn't necessarily just access to greater quantities of the same kinds of opportunities that were already available.

The interpretation of "world" as a noun with actual semantic meaning beyond "a great quantity" in this speech is supported by the context. Anyaoku's speech continues in the following way:

Opportunities not just to put a definitive end to the "armed peace" and its incalculable wastage of resources, both human and material, but also opportunities to step up the fight against humanity's enemies, old and new; political instability and local conflicts; hunger and disease; drugs and the deteriorating environment. It promises to be an exciting world but it will not be all sweetness and light.

Note that the word "world" occurs again in a context where it is not followed by "of", and where it unambiguously acts as the head of a singular noun phrase.

I think a good first step when analyzing an expression of the form "a world of [plural noun]" is to check whether it makes sense as a noun phrase headed by the noun "world" (which has metaphorical senses that don't just express quantity). This is basically the same as checking to see whether a phrase like "an ocean of flowers" is being used to refer to a literal ocean, in which case it would obviously take singular agreement: it's a bit more difficult for world because its meaning as a noun is more abstract, but I think the same principle applies to both.