@ArcherC8 Thank you for replying! However, unfortunately I was mistaken re the model I purchased. It's the Archer A9, not the Archer C9. The reason I brought up the number of devices is that I noticed that the C9 is a dual core processor router and the A9 is a single core. This link: https://community.tp-link.com/us/home/forum/topic/150601 led me to believe that 8-9 devices may be too much for the A9. 

Would this new information change your original answer? In the meantime, I will certainly check into what you originally advised. Thanks again!

@Trahwerdna 

Might want to look at this thread too as it compares the two, https://community.tp-link.com/en/home/forum/topic/157681

A lot goes into 'performance' and 'how many devices' one can 'handle'. First would be how many are using the router at the same time? 10 camera's live connected to a PC via the router sending data continually is not the same as 5 PC's/Laptops connected but inactive along with 5 cell phones that have IP Address but only one in use.

Note that the A9 also had less RAM complicating things.

To me, this initial comment you included might be more important, " I paired it with an Arris router/modem combo device, which previously was used alone and kept getting congested and losing connection. "

First this is that you had the problem before? Second is what do you mean by 'congestion'? I could understand slow loading of web pages, pauses in sreaming or even pixelating, but congestion?

Also the Arris is a modem/router. When you attach a modem to a modem/router, your ISP (unless you own the Arris) must put the unit into BRIDGE MODE, essentially turn off the wireless router function, otherwise you might experience interference.

You can access the Arris using 192.168.100.1 in the URL location in a browser. Usually you can get right in, but you might need the UserID and Password, general default for there is 'admin', but some use that only for UserID and the P/W is 'password' (unless your ISP has changed these). Once on the modem find the LOG and look for errors. More than likely that would cause the drops unless the wired PC did not drop. Then look at the A9's log for reasons why.

@IrvSp I appreciate your reply, I will definitely check into the log of the Arris as I was able to log into admin account at 192.168.100.1. In regard to your congestion comment, I meant that to mean that basically we have 3 children and 3 adults. One is playing video games near constantly via wired connection, the other two will be on their tablets pretty much all day. Then we have my phone, two other adult phones, my computer (which I work from home at the moment) and lastly I play video games from time to time. By congest, I mean using too much of the bandwith? We only have the 100mbps plan at the moment. Hope this helps. Thank you again so much!

@Trahwerdna 

I have a lot of devices on our A20... probably faster and more powerful, but still 12 devices usually. I can count on 2 PC's active and in use or sitting idle with an occasional 'call home' by a program. 1 iPad usually in use and sometimes 2. Add in a Smart TV and we're watching either NetFlix or Amazon Prime for a few hours per day. 100Mbps service and have NEVER had a problem of stuttering/delay/pixelating on the Streaming (generally only needs 10Mbps at most for that), and well as 2 cell phones on-line.

Games may not exchange that much data and usually aren't a load, at least not like Skype or Zoom is.

Unless you are seeing some web sites stop and start loading, or Streaming pauses or pixelation, you probably are NOT overloading the router. However if QOS is working correctly streaming, video, or voice, shouldn't lag.

My A20 has a Traffic Meter and graph, I'll assume your's does as well. It will show you some data that might help you understand your usage:

I can also get the data hourly as well.

As you can see above the 2 iPad's and the Echo Show are big users. Not showing in the above are the 2 PC's, mine used 18.704 GB's and wife's PC, 6.130Gb's. The Smart TV, used 6.327Gb's and it is heavily used.