I'm moving to a place higher in the next city where I am but the village is way up, I might be able to set up solar panel and wind turbine to save myself from spending much for the electricity. Do I need to have at least have a high capacity power supply or I can just keep my 400W?
How many graphics card do you plan to mine Ethereum or XMR? It depends on how many graphics card you have, you can only run 1 or 2 graphics card with 400w if you wanted to build 6 card mining rig you should use 1200w to mine Ethereum or XMR.
And I recommend hx1200i platinum fully modular this is more efficient than not rated PSU.
however, if you only have 1 or 2 graphics card 400w is enough, but AMD cards are power hungry so only 1 graphics is safe for 400w PSU.