IIRC I saw some infantry with smoke. The inf. smoke is more white and has a smaller radius, compared to the smoke thrown by the vehicles.
Art-rounds are determined by the target-type (Anti-armor, Anti-Personal, mixed).
Aircrafts seems to attack with whatever they got, if someone could give more specifics and hints, I would be happy to read more about it.
So far observed:
* A-10s are great vs. tanks, using AT-missiles (AGM65?) first, then the GAU-8 (30mm, nice effects)
* Apaches do not work well for area-targets, using MG and unguided rockets -> with bad results