Hello, can i put GTX 1060 3gb and GTX 1050 Ti 4gb at the same time with 600W PSU? I know that 1060 need 500W and 1050 Ti 300W, but on pcpartpicker.com it says that average wattage is 420W for the whole system. Will my power supply break or should i buy 800W PSU?
You have 3 power draws, not 2. The 1060, the 1050ti and the rest of the pc. That 500w recommended psu is for the whole pc, not just the graphics card. So adding the 1050ti to the pc, you just add its power draw of 75-150w to the existing system, not the 420w for an extra system.
So yes, a 600w psu is fine for both those cards simultaneously, however, that's just 'size in wattage', that's not ability. There's a lot of very cheap and badly built 600w psus that say 600w on the outside, but the insides are much closer to 300-400w at best. They get away with saying 600w because they add in the 3.3v and 5v use total being 600w, when what you really want is 12v rail, as that's what a gpu uses.
So while 600w is realistically plenty for all 3 of your power draws, the physical limitations of the psu itself may not be upto the same level.
I have a 600w Corsair SFX Platinum in my pc. I'd have Zero worries with using it as a psu for your pc. There's also the Circle 600w that was half the price of my psu (less than half actually) that I'd not trust to run a single one of your gpus.
'What you have' is often just as important as 'what you Have' and vice-versa.