In terms of surviving records, it seems there are almost none. In the paper, Recreating the Ancient Greek Javelin Throw: How Far Was the Javelin Thrown?. The authors observe:
We have no direct records of how far the ancient Greeks could have thrown the javelin in their athletic festivals. To our knowledge ... the only reference to the distance that the javelin was thrown in antiquity is from Statius in the Thebaid, where the distance of a chariot racecourse at Nemea is described as being “three times a bow shot and four times a javelin throw: "finem iacet inter utrumque quale quater iaculo spatium, ter harundine vincas" (6.353). However, we do not know the precise distance of the race course, but we can make an educated guess.
The paper cited by the authors above, Greek Javelin Throwing by H. A. Harris, is available to read online at JSTOR. This paper includes discussions of the Greek use of javelins in both war and at festivals which you might find helpful.
In the context of your question, one observation by Harris seems particularly apposite:
... there was one fundamental difference between Greek javelin throwing and our own: the Greeks, both in war and in the stadium always threw with the help of a thong ...
Although some caution in drawing too many conclusions is appropriate since he goes on to note that:
The evidence is very scanty indeed.
Harris may also be of some help in regard to your speculation about the differences between distance throwing and target throwing. On page 30 of the paper cited above, Harris makes the point that:
The purpose of the thong in warfare was undoubtedly to secure extra force and range. Its use involves some loss of accuracy in aim, but the function of the missile spear in post-Homeric ancient warfare was probably that of the machine gun rather than the sniper's bullet.
As regards experimental archaeology, there has been a great deal of research over the years. One paper that is available online as a pdf that might be of particular interest in this context is Efficacy of the Ankyle in Increasing the Distance of the Ancient Greek Javelin Throw, by Steven Ross Murray, William A. Sands, Nathan A. Keck, and Douglas A. O'Roark.
To identify other resources (including many that are not available online, but which may be available to you at a local library), Id suggest running a search on Google Scholar using the terms Greek "javelin" experimental archaeology