wi fi router for gateway

I have 86 devices (not a typo) connected like the doorbell and 5 other cameras along with 44 smart lights, some smart switches, thermostat and a few other sensors and all of this is on the 2.4Ghz side. On the 5Ghz side I have two of the five TV's, three phones phones, three laptops, tablets, Apple TV, chrome cast and google minis.. This was my same setup with the AC-86U and the AX-86U and both handled all of this without an issue.

I can personally vouch for the Asus AC86U that the other comment and I mentioned. But I have also heard good things about some TP-Link routers. A quick search and I see it the TP-Link has QOS. I mention that since with QOS on my Asus restricting my TV's to a 15MB download and 1 up speed caps.  I am able to get four TV all playing 4K HDR videos, a 5th TV streaming 1080P, streaming spotify to 6 wireless speakers with my doorbell camera constantly streaming all the time to my NAS server.
When I ran this same test with the WiFi in the T-Mo gateway I was only able to get two TV’s with 4k videos and one with 1080P and streaming the music since it does not have QOS.

If you give some of the video streaming services and inch they will take a mile. Without that QOS I have seen netflix pull 60 to 70 bursts that messed up other things streaming on the network. I guess my point is with a little router management that has features like QOS it can defiantly help.

I also name the 2.4Ghz and 5Ghz with different names so I can designate two of the TV’s on 5 that can do 5Ghz along with the speakers and the other stuff on 2.4Ghz.
Now this was my extreme test, I will never have four TV’s all running at once with 4K movie streams.

I have had the T-Mo home internet running for two weeks now using an external router and haven't has any issued. My house is kept at 75F and I don't use a fan, but I also have the T-Mo WiFi turned off since the router manages my WiFi.
You mentioned other ISP options. Even if you have a little time to setup and manage the network on an external router with the T-Mo gateway and decide to change later its been my experience that some other ISP's come with very cheap WiFi built in and may even charge you extra for the WiFi enabled gateway. It's always easier to just move your gateway over to the new service and that way you know everything should still work just like it did on the old service.
I will admit that I only tested the built in WiFi on T-Mo's gateway for a day and ran that extreme test for an hour. The built in WiFi impressed me with the coverage and signal quality. It's much better then some other ISP's built in WiFi' units I have seen and tested over the years. But I have a feeling if I ran it longer I might have also seen some of these suspected heat issues others are reporting. My speeds have been  consistent and stable. Labor day weekend will be interesting and I might see a slow down since I live by a lake and everyone is going to be on the lake using that same tower. Maybe I should put everything back onto the T-Mo gateway wifi for this week and see what happens?