@LiamGreenwoodEE slightly confused by a few points You mentioned...
Even CAT5e cable (which is supplied by EE with their EE Smart Hub Plus) is perfectly capable of dealing with 1.6 Gbps traffic, not to say, that any CAT6, CAT6A or CAT8.1 cables will be sufficient, as long as You don't need to run long distances.
In a domestic environment, say CAT6A is more than sufficient, whilst its maximum length it's 100m with 10GBASE-T which means up to 10 Gbps (with CAT6 it will be only 55m for 10 Gbps). CAT8.1 cable will have a maximum lenght 24m for 25 Gbps, respectively 40 Gbps.
I have run CAT8.1 cables between ONT and router, and all 2.5 Gbps links, and CAT6A for links with 1 Gbps, and it's fully working with 1.6 Gbps EE BB (in fact, I have like 5-20x overhead spare on cables 🙂 and it's total overkill...
You mentioned, that there is no way to test over 1 Gbps... Any 2.5 Gbps to USB3 adapter will solve it (and it's cost like 25 to 40 quid), not to say, as myEE app itself, it's perfectly capable of measuring speed to ONT. As OpenReach engineers don't have more than 1 Gbps LAN on their laptops, doesn't mean, that OR or EE is not able to measure or test your line. Pure BS.
Reset of the router is a valid reason for trouble ONLY for previous FTTC, not in any possible way for FTTP. Whilst older FTTC Broadband (Fibre to the Cabinet - than cooper to your home) was sensitive to reset/restart of router, which indicates possible trouble on the line, and You might lose negotiated speed), on opposite is FTTP (Fibre to the Premises - full fibre to your home, terminated in ONT), where you simply have your negotiated line and restart/reset of EE router not really have anything with it...
You can't have 1.6 Gbps package on FTTC, only on FTTP, a.k.a. FULL FIBRE, and OpenReach needs to swap your ONT to a new model if you have only 1 Gbps LAN port on your old ONT, which in fact it's like 5 minutes job...
I have 70+ different devices connected to my WiFi and no problem at all (and I running my router BEHIND EE Smart Hub Plus, which means double NAT), having 1688 / 113 Mbps speed to the ONT.
That said.. 1.6 Gbps package IS WORKING, it's just somehow rushed, and there are teething problems, more importantly, not all EE "Guides" on the phone are capable of dealing with this package, and evidently spreading confusion instead...
