Here what I think of the fire varients
fire pea: its for people who cant aim and its bad compared to the normal pea
fire flower: good for camping out but low damage so this is a strategy character
fire rose: this is a strong rose since it can charge bullets and since homing is screwed up the fire makes up for it
fire chomper: one of the best chompers to use if you don't like swallowing zombies.
fire cactus: this is the strongest cactus because people usually hide or ignore you if you shoot them so the fire damage is useful
BBQ corn: just way better than the normal corn with faster rate of fire and near same damage
centenarian solider: sniper character with low damage that relies on the fire damage
wielder engineer: This is one of the weakest engineers because of the low damage compared to all other engineers
cricket star: rate of fire is good and damage is good but accuracy is a little off
pathologist scientist: this is one of the strongest scientist with 41 damage at close range but seems to be ignored and rarely used which is stronger than the zoologist, marine biologist, and chemist.
drake imp: his damage is good and its accuracy is bad so the fire makes up for it and the mech can beat anyone at close range since it takes so much damage
captain flamebeard: His long range is good since people try to cover and the fire takes damage over time and the close range weapon is weak since it shoots slow and takes little damage