Yes, all working perfectly now as using the Wifi extender at my living hall downstairs (main router on 1st floor) using a LAN port directly connecting a PC desktop ...the speed was ~30Mbps on wireless and now ~80Mbps on wired RJ45 cable connection!

If you used same SSID & password on the Wifi Extender, the devices connected to it may suffer up to  50% slower speed as compared to a direct main router connection. However, it is more convenient as your devices will connect seamlessly to the strongest signal as you move around.

You may try to create a different SSID to check your speed and use the method that gives you the best result.
My preference is always to use wired for non-mobile devices like desktop, laptop, and TV streaming devices (where LAN port is available). Hope this helps too.

A big thank you to delaciox again.. as he provided detailed tips in getting my 'wireless bridge' to work!