Modem/Router upgrade? Lots of devices, poor performance. Help!

I have very limited knowledge so I'm going to list what I know, even though I may not know what it means, and then explain my problem and hopefully someone can help.

- ATT fiber (1000) service

- Running the standard Arris BGW210-700 from ATT

- 2100 sq ft house

- Running all of the following devices regularly via WIFI: 1 Amazon Fire TV Cube, 1 Amazon Fire TV, 1 Echo, 8 Echo Dots, 2 Echo Show 5s, 1 Echo Show 8, 1 Echo Tap, Apple TV 4K, 2 iPhones, 1 iPad, 1 Lenovo Think Pad, 1 Macbook Air, 2 Ring Floodlight Cameras, 2 Ring Stick up Cameras, 1 Ring Doorbell, Ring Security System, 1 August Smart Lock, 3 C by GE smart plugs, 3 C by GE smart bulbs, 7 C by GE smart switches and 1 Arlo Baby Monitor.

I am having major issues with speed. I have a larger(ish) house, but I know people with bigger houses and slower speed internet that have less issues. Now granted they don't have a smart home configured with 40+ devices. In short I constantly run into streaming issues with buffering and my (16) Echos randomly stopping playing my music or start buffering it. I also have issues where apps and my browser on my phone/ipad will just stop working and as soon as I flip off WIFI and go to LTE, it loads immediately. My Ring cameras will sometimes struggle to record montion activated video and the last straw for my wife was that the Arlo baby monitor will crash and stop streaming from my daughters room in the middle of the night.

So here's what I think my issue is... the current modem/router (not really sure the difference so bear with me), says it supports "Concurrent Wi-Fi support for 3x3 802.11n on 2.4GHz, and 4x4 802.11ac on 5GHz)... so I take that to mean that between the 2 frequencies (2.4 & 5) I can concurrently use (downstream as I understand it) 7 devices. By my count I have as many as 43 devices connected to my WIFI at any given time. Obviously I'm not actively using all 3 of my TVs, laptops, ipads/phones all at once, and I assume passive devices like the security system (disarmed), smart switches, bulbs, plugs & smart lock aren't constantly pulling from the WIFI. But it is important to note that I do have all my Echos devices (16) set up to run on various speaker groups, so they all could be streaming music all at once, immediately having 16+ devices pulling from WIFI.

With all that said, I think the 7 channels between the 2 frequencies isn't enough to run my smart home soup to nuts. To be honest I'm not even sure how to connect devices to each specific frequency (2.4 or 5), or if they're even called frequencies, so I could be bottle-necking the WIFI at 4 or even 3 devices. I seriously am a noob if you couldn't already tell.

Someone, please help me understand my issue and if it is what I suspect, is the answer a new modem/router with 32 channels? I've read about how that could help. I see some options out there that are 32x8, but want to make sure that will A.) solve my problem, and B.) I buy one that is compatible with AT&T fiber.

Any help or guidance would be appreciated.