Differences between 2 Teams and 4 Teams Modes
In 2 teams mode has 2 teams which are red and blue which are attacking other colors. For example, red tanks are attacking to blue tanks. When you play 2 teams mode, it will be easy to develop your level because there will be a lot of teammates. Therefore, you can reach 45 level tanks which are 4 tier diep.io tanks such as Annihilator, Battleship, OverTrapper, Auto Gunner and so on.
In 4 teams mode has 4 teams which are red, blue, green and purple that are shooting other colors. For instance, purple tanks are attacking other colors. In a similar manner, red tanks are rushing other colors. You can not level up readily in the 4 teams mode because there are many different enemies in the map. In addition, they want to kill you for gaining points from you. You need to be careful of landmine and other diep.io tanks which are using drones such as Overlord, Necromancer, Manager and so on.
At bottom you will see purple tanks VS blue tanks. I played with blue tank one in this picture. I think this mode is enjoyable for players who want to play with teammates but there are some problems like; if too many bullets in war area, you will have laggy game.