Radically different speeds on the LAN side of the moden/router.

I started off this adventure in January, I started off with with the Home internet step.
First think I realized that there was no port forwarding, Static Ip, and VPN available.  That wasn't going to work for me.  BUT I had also noticed another issue I couldn't explain.  (I will explain with the next part.)

So I moved up to the business version of the internet.  I was told I could do all of the things above with out a problem.

I live ½ a block away from the 5G tower, I get a VERY strong solid signal at all times.  So no issue there.
I currently have an Inseego modem FX3100. (I have tried 2 of the 2000 series as well)
I am only using the inseego for all routing needs, wireless and wire.  (no other router involvement)
 

The problem that i am having is that every device connected to the inseego gets radically different speeds.  This doesnt make a difference if it is only 1 device connected or multiple  they are dramatically difference.  Some will get 400 down, with 96 up,   others get 600 down with 25 up, another will be 150 down with 10 up and one that i cant explain can get 700 down with maybe 2 up.  I even got a new gigabit nic adapter with new drivers for it, and I get the same result (oh and that one is wired only) 

T-mobile cant seem to explain why, but to me it doesn't make any sense.. when My cell phone is connected via wifi to the inseego it gets about 400 down with 100 up pretty consistently.. but everything else i connect is so different.

I has done the exact same thing on all the modems.
if I take all the same computer and run them through my century link modem via a router, they all get relatively the exact same speeds. I realize that is a wired internet via a cellular one,  but the LAN speed should not be effected if I have a device that is constant with the speeds I am supposed to get where nothing else is.

Any thoughts?