I've owned a R7000 for ever, and run with 5Ghz and 2.4Ghz never had slow downs
Laptop with Windoze connect with via 5Ghz to your Network ideally test both R7000 and E6300
While doing a speed test, grab a screen shot of the Wifi screen
This will give us a better idea of whats going on.
The R7000 is capable of 866Mbps connection to like WLAN adapters ie. intel 7260/8260/9260
I still get decent performance in bedroom 20m away through 3x walls
that was 5g between UAP and Iphone 6