Wifi Range on RAX200

I purchase a RAX200 to replace my R8000P for 2 reasons:

1. Take advantage of the higher speed on iPhone X and 11 Pro.

2. Potentially better wifi range to cover existing deadspots in my home

Steps Performed:

Swapped out the old router, same location, same wiring to other wired appliances in my media closet on the 2nd floor.  Performance is wonderful when nearby < 15 ft..  However, the signal strength/range drops dramatically beyond 20-25 ft, which is overall worse off than before.  Logically, this is a real-live apple-to-apple comparison.  Rather surprised that RAX200's range is worse than R8000P from a couple of years ago.  Here's the current configuration after 4 cases involving tier-2 support

1. Downgrade firmware from the latest to v1.0.1.8_1.0.39 (4 releases earlier)

2. Set 2.4 GHz to channel 11 at 1200 Mbps

3. Set 5G-1 to channel 64 at 4800 Mbps

4. Set 5G-2 to channel 128 at 4800 Mbps

Other parameters:

Fragmentation Length = 2306 for all 3 bands

CTS/RTS Threshold = 2307 for all 3 bands

Enable Beamforming

Enable Airtime fareness

Enable MU-MIMO

Enable AX

I do not have in-depth technical understanding of these settings but hope together, they don't compete w/ each other degrading the overall performance.  In my mind, RAX200's range should be at least similar or better than R8000P.  As for now, I have R8000P setup as an AP w/ a switch in front to provide WIFI downstairs w/ a different SSID.  This is obviously not the ideal setup w/ over $800 invested in router alone.  

Please help if anything comes to mind before I give up on RAX200.

Thanks,

Kevin