I think your desire to get as close to the source as possible before settling on an interpretation is admirable and responsible. An enjoyable interpretation’s enemy is a closed mind. An uninformed mind is another.
What you seek, young Skywalker, is an urtext edition.
Peters and Barenreiter both publish urtext editions of the quintet. An urtext edition uses materials such as composer manuscripts and other resources from the period to rebuild a version that is as close to the original notation as a scholar can manage to make it. This is a lot harder than it sounds and requires more judgment than you’d think; so urtext editions may differ from one another for perfectly justifiable reasons. You could ask a Mozart scholar which is “better.” Or you could ask 3 Mozart scholars and probably get 4 or 5 different answers, which is always amusing. Or you could buy a couple (editions, not scholars) and compare them on your own.
Other resources:
Neue Mozart-Ausgabe, Digital Mozart Edition, Series VIII: Chamber Music
Thompson Edition, facsimile of the Scmeidt & Rau parts of 1796
I’m pretty sure Jonathan is on target when he says “there is no one manuscript score of kv407; there are three versions, each built up from sets of parts circulating at the time.” I’m also pretty sure, though, that the discrepancies between the sources are minor.
The recordings you find are unlikely to conform to any one edition because the performers may be adding in or taking out ornaments as they wish. A performer has the right to add or skip any ornaments he/she wishes and this often happens. There is a reciprocal right the rest of have to like or dislike his/her interpretation. Some performers are more meticulous about using only scholar-certified period-appropriate ornaments and others do more of what they like. Both have the potential to be intriguing or annoying.
In fact traditional ways of playing works are often at odds with more authentic, sober, scholarly, or purist approaches. None is good or evil, right or wrong. Some will seem better than others depending on your perspective, which may change over time. A conductor named Furtwangler, for example, had some very bizarre ways of interpreting Wagner. His recordings are still interesting. Some people think Bernstein is an insightful genius, others think he’s a slob. Similarly, no matter what you do, no matter how enjoyable or scholastically responsible is your interpretation, there will be somebody who won’t like it.
Interpretive (as compared to urtext) editions such as those put out by prominent performers have fallen somewhat out of favor since the 1980s because, sometimes, they seem self indulgent; but they often provide intriguing interpretive ideas. Many from the heyday of the romanticized interpretive edition (c. 1850-1950) are available.
