There's a significant amount of literature on this which I'm not going to look up right now, so please excuse the lack of sources; I'll try to edit them in later (they were all found by following the footnotes to introductions to the Mosad Harav Kook editions of the relevant mesechtos, even though the most thorough introduction I believe is that on Eiruvin ...
This is discussed at length in the hakdamah to the Mosad R' Kook Ritva, and in R' Avrohom Shoshana's Ritva published by Ofeq Institute.
In brief, the old Ritva acc. to some is ר' כרשכש. The new one acc. to some is Ritva, acc. to R' Shoshanah it's mostly the Ramah with some others. It's more complicated than that, but that's the Cliff Notes answer.
Encyclopedia Talmudis (הרהור כדבור) says that the Meiri holds this way (it does not mention the Ritva) and any Rishon who holds the Halacha is like Ravina that thought is equivalent to speech in regards to Shema would hold the same for words of Torah.