Poor Wifi Download Speeds - Appears Router Dependent

[ESzczesniak 128]

I am not a very good network guy.  My setup in brief...our house is covered by 2 different routers, as the signal from one starts to fade at the other end of the house.  One is a Comcast router where the cable comes in to our house in the basement, and the other is hardwire connected Lynksys router on nearly the other side of the house on the main floor.  My flight sim room is in the basement, but on the opposite end of the router down there.  This is about 40 feet away through 2 walls.  It gives a weak 2 of 3 bars of signal (i.e., sometimes is just one).  The router on the main floor is about 15 feet away, but through a floor and a wall.  This has a steady 3 of 3 bars of signal.

If I connect to the basement router with weaker signal, I can usually download at 45-55 Mb/s.  The problem with this router is the signal will drop at times.  If I connect to the upstairs router I can download at 1-2 Mb/s.  I just built a new PC, and while setting this up, I did have PC on our main floor...so about 25 feet away, through a cabinet only.  This would download at 120-130 Mb/s.  

I am running Wifi through an Asus Z690-E MB with connected antenna.

So I'm confused.  It would seem signal strength shouldn't be an issue since the slower modem reports a stronger signal in Windows.  I would like to use this as the more reliable connection (it doesn't drop due to signal), but it is very slow.  Both are dual band 2.4/5GHz.  They're both set to "combined" bands so they show up as only one newtwork each.  Any suggestions to getting this to work better?  

Because of the differences in location, I would suspect signal strength.  But Windows doesn't report any strength issues.  So I feel at a loss.

[pgde 571]

You may want to use a dedicated WIFI signal strength tester -- see https://www.techadvisor.com/how-to/network-wifi/check-wi-fi-signal-strength-3803538/ for what software to use. You may be having interference from appliances or other WIFI signals which the software can identify. As far as the dual bands go, while 5 Ghz is faster, the coverage area is smaller than 2.4 Ghz. If you have a laptop and want to check the signal strength, let me know and I will look on my laptop to see which I have installed. All are freeware.