I’m going to do this from memory so I’m going to be very general, but hopefully a little later with some review I’ll be able to give you more detailed information.
Prior to the Council of Trent there were several “Missals” and “Sacramentries” in use in the (Western) Latin Rite Church. One that sticks out in my mind was the Gallic Missal (which was highly influenced by the Court of Charlesmange), and I believe there were other Missals in use in Germany and some areas of Italy and now that I think of it Spain - I think the area of Toledo - that was in use and very popular.
Just an aside, in your studies you might find it interesting of the German influence on the TLM, with its use of symbols (miter, crozzier). It was from Germany that we also find the alter being turned around to face the East, the introduction of Alter Rails and many other things we find in the TLM. Many of these symbols were adapted as the Papacy and Bishops were becoming more monarchical. And an irony of history, the Latin Rite became the Latin Rite (as oppose to the Eastern, Greek speaking rite) because from about the 3rd century, Latin had replaced Greek in the West as the common language, similar to what English is today through out the world. It truely was the venacular, but by the time of Trent it was used almost only in the Church and royal courts and was certainly not common language.
However, as was pointed out the essentials of the Mass had been codified and in use from atleast the 6th cent and perhaps as old as the 4th cent.