What is the highest speed that the Orbi's can handle?

unless your wired you will never get 1gb/s on a single wireless connection.  that service is designed so multiple devices can have high usage at the same time.   a 1x1 connection commonly found in smart phones and laptops will only get a max of 433 mpbs.  thats is perfect conditions. realistly with a good strong signal you will only see around 250-300. newer apple products have 2x2 and 3x3 availble so it can max out the orbi wireless connection of 866 mbps 2x2.  but you can do this on both the router and satellite at the same time with 4 devices you could reach 1gbps speed.  realistic 2x2 speeds are around 650mb/s.  its not a orbi problem its just how wifi works.  5ghz has very little range esp at high speed.  same room line of sight is required for this.  anything else will slow it down.  hook up ethernet to do a full bandwitch test.  as stated earlier also run the qos speed test again.  if it was run with the old setup it will limit the new setup.