How many languages were used by Shem's descendants?

Question

Parshat Noach, 10:31:

These are the sons of Shem, after their families, after their languages, in their lands, after their nations.

אֵלֶּה בְנֵי-שֵׁם, לְמִשְׁפְּחֹתָם לִלְשֹׁנֹתָם, בְּאַרְצֹתָם, לְגוֹיֵהֶם

The posuk after the next one, 11:1:

And the whole earth was of one language and of one speech.

וַיְהִי כָל-הָאָרֶץ, שָׂפָה אֶחָת, וּדְבָרִים, אֲחָדִים

Another question on this site asks why first it says everyone had their own language but then it says all spoke one language before being split; see answers there.

However, the difference between the wording is not addressed there:

What is the difference between שָׂפָה and לָשׁוֹן?

Answer 1

Based on my answer to First it says everyone had their own language; but then it says all spoke one before being split, we see that at the very least Radak (Bereishis 10:5 and here) and RDZ Hoffman understand them to mean the same thing. Many other Mefarshim to Bereishis 11:1 understand the same way (see Ralbag Biur Haparsha, Ibn Ezra I as examples, as they both say this clearly).

However, Ri Bechor Shor has a fascinating understanding of Safah Achas:

ויהי כל הארץ שפה אחת ודברים אחדים – שהיו כולם יודעים ע׳ לשון.

Meaning, that all of the nations understood all 70 languages, and as a result, Safah would mean they could all understand each other's speech, but not the same language. (Rabbeinu Chaim Paltiel also adopts this approach.) Also, see R. Hirsch who comments similarly:

וכיחס "לשון" ל"שפה" - בהוראה המוחשית - כן גם בהוראה המופשטת. השפה היתה אחת, אך הלשונות היו שונות, הוה אומר: הם דיברו שפה אחת בדיאלקטים שונים.

I would love to check various translations, but I do not have many available to me at this point. Hope the above helps.