Skill_MonsterGenerator behaviour

So I would like to use Skill_MonsterGenerator template to make automatically spawn 4 monsters chosen at random between 2 dbr every 30 seconds with a max monsters of 4 at any time.

My questions :
1- Is skillcooldown used in this skill ?
It seems to me that petPeriod is the value that determines the interval of time between 2 spawns.

2- If I set petBurstSpawn 4 and petLimit 4, the first time the skill triggers it spawns 8 monsters instead of 4.Maybe it’s because I have 2 spawnObjects with dbr.
So does it means petBurstSpawn affect each dbr and petLimit is also for each dbr not the global number of max monsters spawned (so first dbr has a max of 4 and second dbr a max of 4 and Total spawned monster 8 ?).
So why is there a weight if each dbr is 100% sure to be used ?

3- What is the difference between a “pet” monster and a “monster” template.I don’t know wich template should be the correct one to use for the spawned monsters.