These do look very nice, looking forward to getting hold of them. It would be great if there were two sprues of each in the box (4 guns plus crew), but looking back at a couple of old artillery sets there seems to be some variance. Boer War Pom Pom guns have 4 plus crew, British artillery have 3, Boers have two guns.
Very good question. As to uniforms, yes they would be very similar from nation to nation but for the color. Same as with most infantry uniforms. Details however will be tricky to ascertain (same as with many infantry uniforms viz. the shade of yellow of the coats worn by the Danish guards or their lace decoration). Artillery train drivers would mostly be hired civilians. French gun barrels used to be highly decorated. As to the guns carriages or their color, no idea, guess we'll have to check some contemporary paintings.