Slow Ethernet and Wi-fi with Apple devices

What Firmware version is currently loaded?
What is the Mfr and model# of the Internet Service Providers modem/ONT 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 RBR and RBS to begin with depending upon building materials when wirelessly connected. https://kb.netgear.com/000036466/How-far-should-I-place-my-Orbi-satellite-from-my-Orbi-router

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 may not 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. Set Short preamble instead of Long preamble modes. Save settings and reboot the router and satellite(s).

Apple wireless issues:
Advanced Wireless Settings both 2.4GHz and 5GHz changed CTS/RTS Threshold to 2307.
https://community.netgear.com/t5/Orbi/Orbi-RBR40-RBS40-V2-1-4-16-mesh-network-drops-connection-to/m-p/1601598/highlight/true#M35230
https://community.netgear.com/t5/Orbi/Have-to-keep-rebooting-my-RBR50/m-p/1658603/highlight/false#M44420
Change the CTR/RTS threshold values for both 2.4 GHz and 5 GHz (2341 and 2345 respectively), changed preamble modes to long preamble, and Set 20/40Mhz Coexistence to 40Mhz only.

https://kb.netgear.com/19668/Link-Rate-and-Transfer-Speed

One User Experience/Configuration:
https://community.netgear.com/t5/Orbi/Most-Stable-Orbi-Configuration/m-p/1941087/highlight/true#M97026