Best rb board to handle 3 mobile internet connections

What is the best mikrotik router

To run 3 or 4 mobile internet connections via

Lte Sim card to ethernet boxes i have
These boxes output ethernet

So i will have three ethernets ewch with seperate mobile internet connection

I want to make a mobile box

And i want a rb board to control the balance for three connections at once to come out of one lan on the rb board

I see some routerboards have pcie cards

Has anyone installed moble lte card into those pci slots

Yup, I have PCIe LTE cards running fine, using the huwawei me909u-521u.

Make sure you are running latest ROS before you start.

Which rb boards are best for this

Also im thinking low power for mobility..

Has any one tried to power the rbboard via two 5v usbs