Here are the different possibilities :

• Value “01” in json set to 300 (or the maximum of zombies you want).
  
• Value “02” in json set to 0.
  
• Value “ZombieMaxCount” in globals.xml set to 0.

The vanilla spawn system will never be activated. If fps go under minimum (“56” value in json) no zombie will spawn anymore.
This configuration is the default one and fit to low populated servers that have no fps problem and which want to only use PvZ spawn system.

• Value “01” in json set to 300 (or the max zombies you want).
  
• Value “02” in json set to 0
  
• Value “ZombieMaxCount” in globals.xml set to 500 (or the max zombies you want).

Be careful, running the two systems can be resource intensive!

• Value “01” in json set to 0
  
• Value “02” in json set to 0
  
• Value “ZombieMaxCount” in globals.xml set to 500 (or the max zombies you want).

The PvZ spawn system will be skip (and should consume very very low resources) but you keep the PvZ loot configuration on zombies.

• Value “01” in json set to 300 (or the max zombies you want).
  
• Value “02” in json set to 1
  
• Value “ZombieMaxCount” in globals.xml set to 500 (or the max zombies you want).

This configuration fits to high populated servers because when fps are too low the PvZ spawn system stops spawning zombies.

With this feature activated, when fps are higher than "56" value, all zombies spawn with other system than PvZmoD (vanilla or airdrop from other mods...) are instantly deleted.
And when fps are under the “56” value, the PvZ spawn system is deactivated and the vanilla system is activated. To reactivate de PvZ spawn system (and deactivate the vanilla one) the fps have to reach the double of “56” value.

Be aware that this feature consumes more resources on PvZ spawn system (to delete vanilla zeds each time they try to spawn) so use it only if you need it (if your fps never go under “56” value you don't need it).

!!!
Fire barrels will not generate zombies safe zone for zombies spawned with vanilla system
!!!

Last thing, don't be surprise if static vanilla zeds (smin/smax) do not immediately spawn when spawn switch to vanilla, the zones have to be repopulated first. And I recommend to use only the dynamic value in the zombie_territories.xml (dmin/dmax) it is less resource consuming when the spawn system come back to PvZ system.