The First Order was one of the best organized military factions in all of the Star Wars universe. Their squad system was amazing because they had a lot of specialization in their ranks. Also since the Stormtroopers were loyal to the first order since they were babies they would very rarely defect.
The standard First Order squad would have ten soldiers in them. They would also have soldiers with different weapons and skills to complement the rest of the standard Stormtroopers in battle.
These specialized soldiers had their own slot in the squad for them, and every squad had one. Depending on the environment, setting, or climate, these soldiers could be a Heavy Assault Megablaster Trooper, Riot Control Troopers or Flametroopers.
Flametroopers
The Flametroopers carried a D-93 Incinerator which was a high-tech flamethrower which could fire up to an amazing 246 feet away. This specialized unit was often deployed on places such as Jakku where there are plenty of flammable things. Their other strength is attacking enemy trenches alongside standard First Order Stormtroopers.
Riot Control Trooper
Their weapons were best designed for riot control scenarios, but they could be useful on the battlefield as well. If they needed to they could draw their blaster rifle and holster their Z-6 and function as a standard Stormtrooper with the addition of a shield.
Heavy Assault Megablaster Trooper
These troopers functioned as the First Orders heavy troopers, and carried the Sonn-Blas FWMB-10k repeating blaster which was probably better known as the Megablaster, (hence their name). These troopers were extremely skilled at doing things like laying down suppressive fire. They also carried the SE-44C which was featured in my latest Star Wars Factions Compared post if you want to know more about it. Both of their weapons had some of the best rate of fire in the whole entire Star Wars universe.