I did my bachelor's in maths in English and my master's in Spanish. I don't think my reasoning is very wordless, but I do think all of my reasoning is kind of geometric. I close my eyes and move my arms around to move a normaliser of a group action or try to trace with my fingers the integral lines of a manifold's tangent bundle.
But as I'm doing these things, I'm often muttering to myself as well, and I may do it in Spanish or English.