so after reading
@SpeedxThunder reply, I tried a few things. And this is my finding.
Static IP glitch will give the best speed if the setting is done in
ONT and you use your
router in double NAT.
If you do the WAN setting in your own router and use ZTE as dumb onu the speeds become a bit erratic.
But in both cases, the speeds are more than the default plan speed ... So that's a good thing.
Another thing, if you try to connect with the PPOE method even after the activation of the static IP, you will be connected with the dynamic IP and the speeds will return back to your original plan speeds. but you get a new IP, this is something useful for people who want to renew the IP for any purpose ..