Canada has its mixed fleet of Leopard 2s due to the successful if complicated program to acquire them during the war in Afghanistan. As the dust settled we had three variants of the same tank. I would rather have a squadron of Leopard 2A6Ms and two squadrons of Leopard 2A4Ms and Leopard 2A4s than three squadrons of Leopard 2A4s.
I don't want to go too deeply, but all three variants have a 120mm gun. The A6M has the longer 55 calibre barrel and some differences in FCS, but the other Leopards have the same 44 calibre 120mm as the M1 family. They are certainly "gun tanks." Protection is higher on the A6M and A4M, especially against the threats experienced in Kandahar.
I won't get into tank disposition here, but Sqns have the tanks they have and train with those tanks.
If there is an operation then the most suitable tanks will be identified and shipped. We have a managed readiness program for the squadrons. A crew could train on a given tank in Canada and deploy on a different one in theatre. Which is how Kandahar went, with the extra hurdle of Leopard 1 training in Canada, Leopard 2 training in Germany and then deploy onto the Leopard 2s in theatre. This is true of most other major combat systems. I was in a Recce Sqn that deployed to Afghanistan. Those were not our Coyotes and Bisons from Petawawa that we fell onto in theatre. Our personal weapons and CP "battle boxes" went with us, but the vehicles were sourced and delivered by others to theatre. There are folks that look after this for a living.
I recall when KFOR took form my tank troop in Petawawa had a panzer (my own) selected to go to Montreal for the operation that soldiers from another regiment would use (and then Dragoons). It went to Montreal for final checks by 202 Workshop and then shipping by the Depot there. I am not sure if that tank actually went past Montreal - I was posted ERE as this all went down and then the fleets had changed to Leopard C2s by the time I was back at the Regiment. But anyhoo.