How should one look at buddhist mythologies and cosmologies from a scientific perspective
This analysis of the Aggañña Sutta includes,
Like the Aggañña Sutta, most of the suttas mentioned above  belong to the genre of religious humour.
15 The humorous language and imagery of such suttas is understandable as they deal with well-established
ideas and norms, taken seriously especially by those who used them to legitimize their affluence
and position in society. Like the Brahmana,dhammika Sutta, the Aggañña Sutta criticizes the brahmins
saying that they have forgotten their past, resulting in their degeneration from an ideal way of life.
The two narratives are, on the surface level of a temporal sequence of actual events, quite different;
but when read as parables using stories of the past to make a contemporary moral point,
they complement each other perfectly well. (Collins 1993a:320)
Richard Gombrich, in his Theravada Buddhism: A social history from Benares to Colombo, remarks
that the Aggañña Sutta is “an extended satire on brahminical ideas, full of parody and puns… As a debunking
job I think the sermon is serious: its main aim is to show that the class system is nothing but a
human invention”; however, “I cannot go here into all the reasons why I think that the positive statements
in the myth are satirical and not meant to be taken literally.”
Should one just regard them as "white lies"
I would regard it as a parable.
There are many parables e.g. about an arrow, or about a blind turtle, or etc.: not a lie, an analogy.
How self-consistent are those descriptions anyways?
I guess you're asking whether the several descriptions of cosmology are consistent with each other.
I think we're supposed to read them as (or read in them) a description of Dharma: and consider their consistency with the Dharma.
According to the Four Great References people should study them:
Without approval and without scorn, but carefully studying the sentences word by word, one should trace them in the Discourses and verify them by the Discipline. If they are neither traceable in the Discourses nor verifiable by the Discipline, one must conclude thus: 'Certainly, this is not the Blessed One's utterance; this has been misunderstood by that bhikkhu — or by that community, or by those elders, or by that elder.' In that way, bhikkhus, you should reject it. But if the sentences concerned are traceable in the Discourses and verifiable by the Discipline, then one must conclude thus: 'Certainly, this is the Blessed One's utterance; this has been well understood by that bhikkhu — or by that community, or by those elders, or by that elder.'