Thank you for the detailed post. But I’m not looking for automation, lighting and other fancy stuff. Also I’m not doing anything from scratch in a new house etc
Just looking for normal stuff to change a couple of switch sets in a couple of places around the house and some Ethernet cabling to shift the wifi router out of my bedroom 
So I will be glad if I could get recommendation of places to buy basic switches sockets etc online (not much is there in Amazon and very costly) and much better if they the popular brands that can get replacement from local shops etc