For game balance, I have purchased 2 Zvezda KV-1s (lovely clean mouldings that assemble in less than 5 minutes). They are still outnumbered by light and medium tanks by at least 12:1. Is this the start of an arms race?
That said, I’m not really sure we should classify any Zvezda tanks as Heavy … crush bridges? on a gusty day they’d likely blow away on the breeze 🙂 Make sure you glue them on bases and maybe put a couple of 2p pieces under the basetex and flock!
Although this isn't about any particular period, scale or set of rules, I mainly use 15mm scale, and for WW2, play PBI company level, or NQM or Megablitz operational level games. My regular circle of enthusiasts also enjoy Russian Civil War and Post War 'semi historical' (AK47 'classic').
I find the Not Quite Mechanised period of the late 30's - where horse transport meshed with armoured vehicles - more fascinating than Late War armour (so apologise in advance to 'SS Panzer-fanciers') ...
Modelling is very important: if it's worth doing, it's worth doing well.