Slow Wireless speeds for Apple devices (RBR50 / RBS50)

[osucoop]

I just installed a orbi RBR50 with two of the RBS50 Satellites.  I have installed the latest version of the firmware for both the router and the Satellites.  The system is up and working well with regards to wifi coverage, but I'm having mixed results with my apple devices and slow download speeds.  I have a separate cable modem and I'm currently getting over 100MB service on a regular basis for all my wired devices.  When running the speed test from the orbi app I get a constant speed over 100MB down.  On several of my apple devices when running a speed test I sometimes get the same speed as the wired devices, but majority of the time I get 8 - 10 Mb download speeds.  I have rebooted the system and connected to different Satellites with same results.  I chatted with support and they have me update the DNS setting to point to google DNS, which provided no difference in results.  The next steps according to support is to reset devices and reinstall the latest firmware.  Is anyone running into this issue and if so what steps did you take to resolve?

[FURRYe38]

What Firmware is currently loaded?
What is the Mfr and model# of the ISP modem the NG router is connected too?
Is the Orbi system operating in Router or AP mode?

What is the size of your home? Sq Ft?
What is the distance between the router and satellite(s)? 30 feet is recommended in between them to begin with depending upon building materials when wirelessly connected.

What channels are you using? Auto? Try setting manual channel 1, 6 or 11 on 2.4Ghz and any unused channel on 5Ghz.
Any Wifi Neighbors near by? If so, how many?

Try enabling Beamforming and MIMO(MIMO may or maynot be needed) and WMM. Under Advanced Tab/Advanced Settings/Wireless Settings

Try disabling the following and see:
Armor, Circle, Daisy Chain, Fast Roaming, IPv6 and Set 20/40Mhz Coexistence to 40Mhz only. Save settings and reboot the router and satellite(s).

Has a factory reset and setup from scratch been performed since last FW update? 

[heathweather]

In addition to all of the excellent suggestions @FURRYe38 has made, as a sidenote, I've had intermittant results with apple idevices.  I've had an iphone XS and an iphone 8 side by side, run a speedtest, one at a time, using the same server on speedtest, the XS sometimes seems to be stuck on b/g/n, it caps out at 80mbps, while the iphone 8 consistently performs much higher - ~300mbps , I've got 1GB service. Both devices are iOS 12.4 , so I am unsure as to why the XS is somewhat hit and miss, while the 8 is rather consistent.