'We don't know the most fundamental questions about Napoleonic artillery, like were 12lbers better than 6lbers?'
Sure we do. It depends on the mission, the availability of the caliber(s) required and what you actually intend on accomplishing. Napoleon, himself an expert artillerymen, clearly favored the 12-pounders, his 'pretty girls,' but would use either what was available or what he believed was suitable for the intended mission. And for other 'fundamental questions about Napoleonic artillery' there are enough primary and credible secondary sources available to find out.
'...so I think it will be a long time before we figure out how French instruction in drawing made a difference on the field.'
I would highly recommend that you read Ken Alder's Engineering the Revolution for information regarding the curriculum of the French artillery schools from 1765 on. The curriculum, which was both theoretical and practical, was modified with Gribeauval's sweeping reforms of the French artillery arm and he also had professional schools opened for the French artillery NCOs.
Artillery is both an art and a science. The 'art' portion is how you employ your artillery in the field. The 'science' portion is the technical education needed in order to be competent in the artillery branch. Napoleon commented what he was able to do technically after completing his artillery education: 'If there is no one to make gunpowder for cannon, I can fabricate it; gun carriages, I know how to construct. If it is necessary to cast cannon, I can cast them; if it is necessary to teach the details of drill, I can do that.'
What artillery officers studied in the French artillery schools, which the Austrians modeled theirs on by the way, and which predated any other European artillery schools (the first was formed at Douai in 1679) was basic algebra and geometry, calculus, rational mechanics, hydraulics, the principles of machines, plus physics and chemistry. Ballistics and analytical calculus were also studied as well as technical drawing, applied mathematics, and descriptive geometry. Technical drawing was important in the design and application of new weapons, carriages, and vehicles especially since the Gribeauval System set a new standard on production tolerances and uniformity of design and production. Without being able to draw technically, the artillery officer would be out of his depth when required to supervise artillery and small arms production, which were the responsibilities of the artillery arm.
As the discussion did mention the Russian artillery arm, this level of education, if any at all during the period, was not this intense nor did it cover as many subjects. The Prussians had no artillery school until 1791 and the Russian artillery school as far as I can see was not formally structured until 1820. The British and Austrians had excellent artillery arms because the officers were excellently educated and trained, as were the French. You cannot claim to have an excellent artillery arm without educated officers and both the French emigre General Langeron and Sir Robert Wilson remarked on the low-level of education the Russian officers had. This was partially remedied starting in 1807-1808, but it takes time to build up a trained technical arm and the Russian artillery did not reach the competency level of the British, Austrians, or French until well after the Napoleonic period. In my professional opinion as an retired artillery officer, the Russians are still behind technologically in artillery and still rely on quantity over quality.