@sk1pmcgee 

You may be having multiple issues with your Deco mesh: Internet speed between Main Deco and Comcast modem, and also location of Satellite X20s might not be optimal -  reducing speed on devices connected to Satellite Deco. There is also a possibility that your mobile devices try to connect at slower 2.4GHz WiFi band instead of WiFi5 or WiFi6. Finally, it might be that your 2nd floor X20 connects to basement Main Deco, with weak backhaul signal between them.

These are too many to deal at once, so maybe it'll be easier to start with troubleshooting the most obvious one. Your PC connected by Ethernet to Main Deco should be getting close to gigabit speeds (850Mbps-900Mpbs to be exact). Having just 200Mbs is not right.

You haven't said that, but I am assuming you run your Deco in Router mode. If yes, check the QoS value in Deco app and increase it to at least 1,000. See that document for more info: Using QoS feature of Deco

If that does not work, more troubleshooting will be required. Please tell if your Comcast modem is just a modem, or it is router (modem+gateway). If it is just a modem, do you still have netgear router that can be used as router attached to your Comcast modem? 

@Alexandre. 
 

hardwired pc now reading what it is supposed too.  See attatched image.  What do you think next step is to check?

wifi on my phone on 1st floor (not basement) still reading 30 mbps standing right in front of deco unit

@sk1pmcgee 

The next step will be to establish baseline of X20 WiFi performance. 

Power off Satellite X20s, leaving just Main Deco running. Take smartphone you are (will be) using for all speed tests and bring it to where Main Deco is. Keep smartphone at 3-6 feet away from Main Deco and run speed tests on smartphone multiple times. I would recommend using Ookla speedtest app. Note best result.

Turn off 2.4GHz on Main Network in Deco app, so that band steering is disabled, re-run speed tests with smartphone connected to 5GHz exclusively. Note best results and also if there is a substantial difference between two sets of speed tests.

What you'll get will be the best Deco X20 can do with smartphone you are using for speed tests.

Let me know when you've done that, what results you've got, and next will be evaluation of Satellite Deco X20 placements and their connectivity to Main Deco.

By the way, floors in your house, are they made of wood or of concrete?

@Alexandre. 

Welp looks like I am the one to blame.  I had 5 Ghz channel off this whole time.  Turned it on and tested my iphone next to main deco and 700mbps.  I feel super stupid.  iphone now at 500 mps in Living Room.

Woohoo!!

Thank you for all the help!!