"(LACTANTIUS c. 240 to 320): ...Et quamvis alios postea innumerabiles per ipsum creavisset, quo angelos dicimus...' - (Latin Text of Divinae Institutiones Book 4, Chapter 6, Section 1. MGL.)
Does Latin ( alios ) mean 'another'?
Or does it mean 'other'?"
According to Lewis-Short Latin Dictionary and John C. Traupman's Latin-English Dictionary, the word can mean either "another" or "other" or "different" along with other denotations in determinate speech contexts.
"Is Latin ( alios ) the equivelant of Greek ( ἄλλος ) '...another (numerically) of the same kind and quality...'?
TRENCH says: '...( ἄλλος ) identical with the Latin 'alius' ... But ( ἔτέρος ) equivalent to the Latin 'alter'..." - (Page 357 SYNONYMS OF THE NT)
Is Latin ( alios ) a plural word?"
ALIOS is accusative masculine plural of ALIUS.
"Could it be (paraphrased): '...created innumerable others of the same kind, whom we call angels...'
Or would that be stretching it to far?"
I could be wrong, but I don't think "others of the same kind" would convey the notion behind the Latin ALIUS/ALIOS. IMO, the word usually stresses difference rather than sameness. See Lewis-Short at Perseus for many examples of how ALIUS is used.
You also write:
"The other two translations render it this way:
(LACTANTIUS c. 240 to 320): '...and though he later created countless (OTHERS), whom we call angels...' (Divinae institutiones 4.6.1)
(LACTANTIUS c. 240 to 320): '...And although He had afterwards created by Himself innumerable (OTHER-BEINGS), whom we call angels...' - (ANF Roberts & Donaldson)"
I like the second translation best since it preserves subtleties like the use of creavisset, etc.