@Kevin_Z Thanks for offering the remote session. 

I'm still continuously testing speeds on all devices I have and it seems that more than having low speeds all the time, the problem is inconsistency. 

Sometimes, I see my Mi4 (which has 5GHz band) getting ~80mbps download and my same iPad also getting ~80mbps, but I also see 30mbps on some runs. 

The main reason is that, since I switched wifi, I have been getting some complaints from members of my family (who use their devices on the same wifi) saying that the speeds have been slower when browsing etc., since I changed router (from tenda to new tplink c7). This is why I started testing and found these inconsistencies with speeds in different devices. Could it be that android devices have a problem with this router? has there been an issue like that?  

Edit: I will let you know the details for the remote session based on my availability today. 

Edit 2: Could the problem be due to the fact that there are many devices connected, so, the speeds are less based on that + other interference? C7 does not have MU-MIMO right? so, more connected clients on both bands = lesser consistency - is this a valid conclusion? 

@Kevin_Z 

Ok, so, My desktop is turned on, ethernet cable connected to desktop and verified that I get internet (using PPPoE). Speed check: ~190mbps up and down in my desktop (wired connection) - all good so far. (My ISP connection line is 200mbps)

If I connect and test each device individually - over many tests, it seems that my oneplus has much lower average speeds when you isolate and compare it vs others. iPad is the most stable - it reaches max of 90mbps up and down whereas, both my android reach max ~200mbps upload, but far lower download speeds. One problem I frequently see is, the speeds start off high, but it goes down fast and never goes up again during the test. Is this because of the client (connected device) or the router? 

MacBook speeds are stable but the slight connectivity issue is still present. I will test it again now. 

My ISP supports IPv6, so I tried enabling that - my wired connection speeds dropped a little bit - I'm not sure if this has an effect on WiFi speeds yet, but that test is on my todo list. 

Regarding the remote session, since the laptop is not my personal one, I can't do a TeamViewer session, unfortunately. But I will gladly report screenshots/data results if you need.

So, far I don't know if any other alternatives to A7 in this price range. So, despite these issues, I'm leaning towards taking a chance on it based on the assumption that the speeds that I'm seeing on my phones and iPad is low because they are old devices. Because, my macbook (still old, 2013 model) but good hardware consistently gets ~150+mbps if it gets connected to 5GHz properly.

Are there any other tricks - like QoS settings/NAT/IPvX that I can play with to get a better understanding of what's happening? I have tonight till I can cancel the refund and keep the product.

Sorry for the double post again, but I felt like this (summary) content deserves a separate post. 

So, I've decided against returning. I've canceled my return-for-refund request. Why did I do this? Poor performance in wifi alone for specific older generation devices skewed my opinions of the router. Also, don't trust speedtest (okla) anymore. It's plain ISP-rigged crap. One of the main reasons why I concluded that my archer C7 is better or in some areas at least equal to my previous router in wifi capabilities is that, in generic speed test that don't just test with the closest server, I found drastically different results when compared to the speedtest (ookla) results. If anyone is reading this and if you are comparing wifi results between several devices, try websites like testmy.net, dslreports, google's fiber net speed check, google's stadia speed check etc., - all these services have servers at different result and will give you a more holistic result rather than just up/dl from the closest server which is a useless real-word metric. Based on these tests, I found that the C7 is indeed better in almost all the test runs than my old router - check on 3 devices where I had the most problem - so that's ~40-45 data points - not a lot, but for home testing, I think this is more than enough. 

Then one thing my old router (Tenda AC6 (Broadcom chip model) is better than C7 is it's range - both in 5GHz and 2.5GHz, because of this I plan to use my tenda as a wireless repeater later on when needed. 

The issue about my laptop not picking up 5GHz immediately does not seem that big of a problem for me. All I have to do is turn on the laptop 1-2 mins after the router is turned on after that, I pretty much connect to 5GHz band instantly and my laptop has never had any speed-related problems with wifi. It was only my android phones + iPad. What I learned is, if you are checking 5GHz stuff on older devices, don't rely on speedtest (ookla) alone! Use a variety of tests! You will be surprised! 

Thanks, @Kevin_Z, and @ArcherC8 for your suggestions. I definitely learned a thing or two about routers and speed tests in trying to solve this problem! haha! :)