RAX35V2 Walmart special

I've purchased the same ROUTER from Walmart.

I didn't checked on the Internet about that router before purchasing -  I just saw the price ($112) and immediately decided to get it.

My previous router was Netgear AC2350. I did not have any issues with it until recently.

In the last month, I would check my Internet speed (from Xfinity) around 7:00am. It's about 489mbps.

Cool, but...

Around 10:00am it would go to about 50mbps.

After a few days of similar results, I've called Xfinity and they sent a technician to work  on my issues. After checking all my connections, the technician figured out  that my problem was not with Xfinity or my Arris gateway/modem, but with my Netgear AC2350 router.

My AC2350 had all recent updates; therefore, I've decided to get a new router.

I got RAX35v.2

The instalation of RAX35v.2 was, more or less, easy, and the wired computer showed constantly my internet speed at around 400mbps. I was happy with it, but...

I've noticed that it shows only one network - Netgear...

I did not see a network of the 5 GHz band. 

Now, my biggest issue. 

I've re-installed my Netgear Mesh extender AC2200 EX7300.

I was not too dificult to re-install it with the help of Netgear App, but...

With my previous AC2350 router and the  same Mesh extender EX7300, I used to get about 230mbps around the Mesh extender by using the 5 GHz band.

Now, I can get only about 96mbps.

Is the signal from RAX35v.2 weaker than from AC2350?

Should I purchase a new Mesh Extender, like EAX80 or something similar?

Maybe, Dual-band AX1800 Add-On Satellite (MS60)?

Or, maybe, I should return RAX35v.2 and get 

the NETGEAR Nighthawk AX1800 Dual Band Mesh WiFi 6 System, 2-Pack (MK62)

Thank you for your help.