How should one look at buddhist mythologies and cosmologies from a scientific perspective

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 [3] 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.'

Buddhism speaks of Arya (noble) Experimentation. It's main purpose is to get rid of suffering. Therefore, through Arya Experimentation, one observes such suffering and concludes (if done thoroughly) that all things created, change and perish, thereby is sorrowful and causes suffering by nature. This is called the Four Noble Truths.

Science encourages such experimentation. Science encourages to note the observation and science notes the conclusions.

Science looks for a solution if the conclusions contains symptoms of a problem. Buddhism does the same. The path to finding the solution in Buddhism is the Noble Eightfold Path

... reconcile with modern science? ...

Modern science is always changing with new theories and discoveries but Buddhism is presented as eternal or timeless which is valid in the past, present and future. Hence these two cannot be fully reconciled. Since is refinement of theories and models getting closer to the truth while Buddhism is based on publically released ultimate realities. As science advance many of the concepts are in harmony and while there are perhaps hardly any scientifically proven discoveries which contradict Buddhism.

... which again share (too) many similarities with the hinduist ones ...

If you compare Hindu cosmology with Buddhist cosmology (especially Buddhist cosmology of the Theravada school) there are wast differences. In Hinduism there is a creator but in Buddhism the universe goes through expansionary and contractionary phases.

... reconcile with modern science? ...

You cannot. But Buddhism has a theory of cyclical phases of the universe like the big bounce theory, parallel universes (see Parallel universes by Piya Tan), evolution, etc.

Also see: Buddhism and science, Buddhism and Modern Science - by Dr. Granville Dharmawardena (especially the highlighted areas), Is Buddhism the Most Science-Friendly Religion?

... including Karma could be partially gained/observed through meditation. ...

Meditation (especially samatha) can lead to psychic powers / supernormal knowledge like clairvoyance (divine eye) which can be give insights to the working of Karma. E.g.

Thus, by means of the divine eye, may I see beings passing away and reappearing, and how they fare according to their karma.’

Source: Nimitta Sutta similar passage in Kaya,gatā,sati Sutta, Samanna,phala Sutta, Maha Assa,pura Sutta, Kevaddha Sutta.