Yo
i wanna mine ETH mainly and sometimes some new currencies that use GPU for mining
i have money up to 2 video cards kinda
i think i will get 2x RX580 8GB even tho they are expensive for me

wondering, how much profit will i get with it?
how much power i need in my PSU to run those cards (I think the base computer will take like ~100W-200W)
and if its profitable, how much profit will RX560 4GB make? thanks.
Make sure you are getting those power specs right. I have rarely seen a base machine that runs off of 200W. Or did you get that spec from a motherboard or something. Older computers even, with nothing but the board and the output devices, without any carding need 400W or more.