That all depends. Technically, there are only 2 proper tanks among them (Warchief Assault Tank and Pointman Scout Tank). The others are really just armored reconnaissance vehicles, infantry fighting vehicle and other such.
But in terms of how realistic the design is, the CS Odjur, Urga Bkolos 2100 and Prizefighter Tank are all good enough to be completely real.
The second place in this realism would have to go to the Warchief Assault Tank and Pointman Scout Tank. While their designs look somewhat odd, I can believe that some nation would put random equipment containers on the turret to end up with seems to be a weirdly-shaped turret and that some nation might create a low-cost light tank that could be useful in some situations.
The last place goes to the Imperator Bavarium Tank for having a completely fictional shield and a complete nonsense double-barreled armament.
Imperator Bavarium Tank
CS Odjur
Urga Bkolos 2100
Prizefighter Tank
Warchief Assault Tank
Pointman Scout Tank
