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.
There are mining calculator available in the online. You can check the profit calculation with that by selecting your pc specification such as cards you gonna use, hash rate of the card, electricity cost in your location. These all together you can calculate the bitcoin or altcoin mining cost accordingly.
In the below link you can find the calculation for eth. Check you coin you want to mine and search it.