Anecdotal data, based on a sample of 1 (aka me). I'm originally Polish, but I would say my mother tongue is English. I also learned Latin as a kid/teen. Then learning any other languages is much easier, I also learned German and some Swiss German dialects. I can also do Spanish, Italian, French, Dutch, Czech, some Serbo-Croation. I think being Polish makes learning languages easy - as we have a lot of creations in Polish that do not translate easily to other languages. I think in my case it's the same part of brain that processes both human language and computer language. My brain can do another fun party trick: I never learned cyrillic, but I can read it just fine, my brain does like pattern matching and statistical analysis when reading cyrillic.
I also learned to think in hmm "concepts", and then apply a language of my choice to express them. It's a fun skill to have :) Obviously works of Chomsky are great, especially exploring if language evolves mind or is the other way around, does mind evolve language? [let's skip his rather controversial political views lately].
I was blown-away on holiday to Croatia. It was so unexpectedly relatively easily understandable after Czechia, Austria, and Slovenia. I was all, "What just happened!? Shouldn't this be something more like Italian?"
It took only a month for me to be able to communicate in Ukrainian with my ESL students, you're totally right about Cyrillic. And I too think in concepts but switch my brain to express them externally via language, whatever that language may be at the moment. I am terrible at translating OTOH, so unnatural!
But it has it's limits, I got to a point after German and Norwegian that I thought I harbored a super-power. Then I went to school in Hungary ;) I also had an ESL student from Lithuania, yep incomprehensible.