Can I connect WD 2TB portable HDD to the USB port of AXE75 / AX73 --> Does it work fine properly?

Can any one let me know how many smart devices AXE75 and AX73 can handle? I have about 70 smart devices at home.

Hi, Currently I am using Hitron Coda modem in Canada. I am planning to make it bridge mode and use AXE75 or AX73 as my wifi router. I usually reboot my Hitron Modem once a week. So my question is when