I prefer grand tactical rules, and gearing up for DBN on 60mm wide bases, 2 guns per stand and the stands are likely to get grouped in grand batteries. So yes, I'm looking for a fairly close match. Doesn't have to be exact.
The biggest visual key for me is if the wheels are close to the same diameter and thickness. Carriage or barrels have a bit more leeway. Battle Honours for instance has wheels that are too small and too scrawny. (They do make lovely destroyed guns for marker stands though.)
For the Russian ones I have on hand that look MiniFig-ish:
12-pdr: wheel 12mm D, 1.5mm W; carriage 25mm L, 8mm W.
6-pdr: wheel 11.5mm D, 1.5mm W; carriage 24mm L, 7mm W.