@AlokJain 

Hi,

It's difficult to judge the situation without knowing how far the Wi-Fi router and Wi-Fi adapter are apart from each other and whether any objects are located between them.

To verify the Archer TX20U Nano is fundamentally working, it's speed should be tested with the laptop being placed right next to the Wi-Fi router, like 1 or 2 meters apart.

AlokJain wrote

... When I am doing a speed test using my laptop's Wi-Fi 6E card, I am getting speeds up to 300 Mbps over a 1 Gbps plan, whereas when I switch to the TP Link Adapter, the speeds decline to 100 Mbps on the same 5G connection. 

That's not really a fair comparison. The antennas of Wi-Fi cards built into laptop computers are commonly installed near the edges of the lid (i.e. in the bezel of the screen). Such antennas are something like 10x to 20x larger in physical size than the super-tiny antennas used inside "Nano" USB adapters.

  @woozle I have tried even keeping just besides the router which is 0 meters from the router

  @AlokJain 

If you are next to the router, then even the 300 Mbps of the laptop's Wi-Fi 6E card seems really low for a 5 GHz network. There must be something that's not right.

Can you please look up the "link speeds" of both, the TX20U Nano and the laptop's Wi-Fi 6E card within the "Properties" screen of the Wi-Fi connections?

  @woozle I opened a separate thread on the overall slowness of the TP Link AX300 XX530V Router. I am not getting sufficient speeds on LAN or Wi-Fi, either on the ISP-provided OLT or when I have converted the TP-Link AX3000 router to the primary OLT. Link to the thread is Slow Speed on TP Link XX530v main router over Airtel 1 Gbps Plan. Please help me on both the things if possible or redirect me to the correct person or forum where I can provide substantial evidence to the ISP that the slowness is on their backend part and what they have to rectify to resolve the issue.

Laptop Wi-Fi Adapter

Speed Test Result on TP Link Adapter

TP Link Wifi Adapter

TP Link Adapter Settings

Laptop in built Adapter Settings

Speed test results on Laptop Wi-Fi