During the NHL playoffs I bought a 100' Ethernet cable to go from the TV to the router.
Wi-Fi always seems to die during a breakaway!

We handled this same problem with Ethernet over Power adapters. Works great.

Thanks all for the help.. (I have fiber so coax adapters won't help me).
Here's the numbers and solution for me:

My smart TV was doing 5 MBPS natively. Ugh - shoot it now... So firestick...

Firestick on blended Wifi (2.4 + 5.0 bands active) was 16 MBPS - better but meh.

Firestick on 2.4 GHZ band only (split SSIDs between 2.4 and 5.0) was 54 MBPS
Firestick did not see 5.0 band no matter what channel I tried..

Firecube On sale prime days) on 2.4 (default) also 54

Firecube -> Sees 5.0GHZ band -> 361 MBPS ! Yeah that will do..

So 5 -> 361, I think I will have less drops ;-)

Note that networking is magic to me, don't understand why mixed bands under the same SSID was killing speed so much vs splitting SSIDs per band. Maybe a slow device ruining speed for all, but then*both* sides sped up once separated.. anyway, cool.

Fiber only runs to your house and terminates at an ONT.

It comes out of the ONT as CAT5/6 or coax to your router.

Your router distributes ethernet over your homes existing coax.

Your old set top boxes (which I assume you got rid of or never had) communicate over ethernet carried by coax.

That is why MoCA adaptors work.

As to why you combined is slower, devices that can auto assign 2.4 or 5 are more likely to connect to 2.4 because its range is larger, 2.4 for distance, 5 for speed.

Once it connects to 2.4 it stays there.

I'm assuming you are comfortable digging around in your routers backend?

If you get curious check the power levels default settings.

Betting they are equal. You want 2.4 power lower than 5 to mitigate devices defaulting to 2.4

It is amazing wifi works as well as it does. Especially with microwaves and other equipment dumping noise out there.