My own take on- and summary of SMGs, carbines and assault rifles. Might help some players with confusion. Others might disagree and correct me.

Carbines are a nice compromise and hybrid between the assault rifles and SMGs. SMGs too weak mid-long range? Assault rifle hip fire accuracy sucks? Carbines meet in the middle.

Carbines are my favorite. They have decent ADS speed, decent at long ranges while still having a good hip-fire accuracy. I'm currently rocking the QBZ-192.

Overall, carbines are like shorter and more maneuverable versions of assault rifles, without having to go all the way to SMGs on the other end.

SMGs: specialty is short range. Super fast ADS, fast draw and good hip fire accuracy plus low recoil. But lower damage per bullet, lower bullet velocity and steeper damage/distance reduction curve.

Carbines: More all-rounder around mid-range, give or take. Between the SMGs and assault rifles in all aspects.

Assault rifles: specialty is mid-long/long ranges. Slower ADS. Slower draw speed. Higher recoil than carbines and SMGs. But has higher damage per bullet, higher bullet velocity and a less steep damage/distance reduction curve.