Internet speed issues

Hello,

I am not sure where to go with this question as I have exhausted many of the options.  so putting this here for someone to potentially help pinpoint where the problem is. 

i have (had)  the PW7 gateway setup with a deco mesh network for our home. The plan was 1G mbps. We noticed that internet speed on TV streaming and laptop(s) is very weak. 

However, the speed on the iphone (as measured by the ookla app) was really good. Same when u measure with the Cox app. 

called cox and they recommended to move to the pW8 model and the 2G plan. I did. 

i was suspicious that it was going to resolve the issue because the iPhones were always registering very good speed. if the router or the plan where the issues that would not cause the iPhone to be good and the computers and the TV to be bad. Because we were reading 800mbps on iphone  vs 50mbps, i don’t think it is due to the wifi6 vs wifi5. 

I thought that it might be the computer and the Wi-Fi adapter so I tested multiple computers as well as a wired connection and in both tests the speed was not improved. 

I am baffled by how the iPhone can read a faster speed than the other other equipment in the house and I’m wondering where there is a the solution available to us.

Has anybody experienced this issue before any help is appreciated