@SayeemAhmed 

If you want to buy X60, because you are not happy with performance of your Deco mesh, you should first figure why you are getting message "Abnormal WAN port speed." This message says your Main Deco negotiated just 100Mbps speed over Ethernet cable to ISP modem/router. Instead of standard gigabit speed.

If you manage to fix the problem (usually, replacing cable does that) and your Internet speed provided by ISP exceeds 100Mbps, you will see improvement with your Deco mesh.

Just replacing Main Deco X50 with X60, which you can do, but not fixing Ethernet cable issue will not bring speed improvements you expect to see.

  @SayeemAhmed 

With Deco mesh it is more important what features Deco unit supports than hardware version. The best way for you to test would be to borrow X60 from your friend, add it to your Deco mesh as Main Deco and see if all features you do use still available in Deco app. 

As for this specific hardware V2, it is quite old. Yet, don't expect newer hardware (V3 or V4) be necessarily better and faster: because of chip shortages during COVID and getting whatever substitutes are available, and because of inflation that requires cost management for components it might be possible that older X60 V2 is more powerful than newer X60 V3 and V4.

I am only speculating here, TP-Link does not offer full set of hardware specs and their performance benchmarks, but we are living in a time where manufacturers may degrade newer networking gear performance to hit cost, availability or power consumption goals.

To summarize, I would be more worried that this X60 unit is functional and that it provides all features you currently use. If you tested and it does, and your friend offers X60 with good discount, I would go for it if I were in your place.