assault engineers are only unique with the ability to use assault rifles but since all assault rifles in the game are BR5 except for the BR4 mkb42(M) and BR2 mkb35/III event/BP guns there is no use for assault engineers on low BR since 6 engineers are worse than 4 engineers + 1 AT and 1 assaulter.
They are very useful on BR5 though but if you only play on low BRs than there is no meta advantage for using Soviet assault engineers other than having fun.
The assault engineers are good at high BR but kinda pointless at low BR.
I would use a regular engineer squad with the AT and radioman for the versatility. Make sure you use the engineer squad with the molotov launcher cause not all the engineer squads have them. You can also put gold order engineers, AT or radiomen in the squad for a 20% experience bonus. You get no XP bonuses with the assault engineers.
If you are playing BRIII the SVT38 is a very good semi auto rifle for the engineers, at BRII the Winchester lever action is very powerful and fun to use. Also at BRIII the Panzerfaust 60 is fairly good for the AT soldier, and you can put both an SVT38 and a Winchester on the radio man.