The KV 2 Has the default KV Chassis, which means it is weakly armored (for BR 4.3) so always try to have cover (For exsample a house or a rock). The KV 2 isn't fast, the armor will rarely safe you and the gun handling is horrible.

so what makes this tank great? In short: The gun. The gun is what made this thing what it is now (mostly a meme), yes of course the silly design aswell but the fact that it one shots all tanks at its tier is what made it that popular. So of course the only thing you're really gonna need on that thing is the gun right? in short (again) Yes. Yes it is. Unfortunately.

As I mentioned before The HE shells are Better. but that's not always the case, As an exsample the Tiger is much more armored as a regular medium tank. The HE can't get through the armor of the heavy tank, so in this case AC is recommended, it can penetrate the heavy armor easily and destroy the tank or cause a fire. but against medium tanks, light tanks and SPGs The HE is More effective

Since the HE has become so much more unreliable with the recent additions to the tier of the KV 2 and some changes to the way HE works in the KV 2, this has lead to the changeover from mainly HE to mainly AC. Because AC is much more reliable at destroying your enemy (especially against the British, since they've got tanks like the Churchill and others). There's also an APCBC round, it gets an increase in penetration but suffers from a lower shell velocity, (which only makes matters worse considering you're firing a short barreled 152mm Howitzer) because of that the shell becomes much more harder to hit than the AC shell, use the APCBC when something absolutely, surely, definitely needs to die.

Considering the things from earlier, there technically aren't many opponents the KV 2 struggles with. The main downside of the KV 2 might actually just be its horrible gun handling and the decades of a reload. You can pretty much one-shot any tank in the game but your reload is the big killer, Just stay out of sight after firing and ensure a safe reload spot (preferably behind/near teammates)

I hope This helped increasing your skills in the KV 2

Good luck in the Fields!