it seems, it is more a problem of how YOU want to show/use it. Should it have more of a realistic touch or should it be a bit more functional?
realsitic would be, to have it a) seperate and maybe even b) two times. One in a settled version with all that shooting stuff placed around and one in a transport version, where everything is pcked and "in line" for moving.
So ... i think it depends on, what You want to do with it more often. Just show and tell or gaming ... or both ^^
On the battlefield I have seen all ... yeah ^^ ... I mean, I have seen placed cannons with horses waiting patiently behind it (patient even while firing ^^) or the crew placed motionless on the same base, loading their cannons while being transported in the line for moving out the army.
But then - if there are rules for moving, I think it should be seperated (at least crew and gun). The other option is, to always put everything seperately, crew, guns, horses, caissons and the like. So You are able to place it according to the situation in whatever set-up or rule or game. More work, more effort, more rewarding
best wishes
Drachenklinge