It's all about draw of luck and lottery of silicone so just pick any batch will do. 

The non-Z board overclocking will be disabled by BIOS/windows update. If you can afford a K CPU, you should be able to afford a Z board as well. I know can save some bucks, but why choose to have the limitation. 

Intel Cracks Down on Motherboard Vendors Offering Overclocking on non-Z Chipset

Now, I’ll share a secret imparted by the folks at ASUS who gave several reviewers some tips on overclocking the retail stepping Haswell chips: Set Vcore to 1.20 V. Set all cores to 46x (which would be a 4.6 GHz overclock), save & reboot. If the system boots past the UEFI and either begins to load or, ideally, makes it into the OS and is stable, you have a 50th percentile or greater chip on the Haswell overclocking-ability bell curve. If it won’t at least boot there and make it into the UEFI, you probably have less than a 50th percentile chip. You can expect chips in the lower 50th percentile to top out in the 4.4-4.5 GHz range at 1.25 V.

If your chip will boot at 4.6 GHz and 1.25 V, that’s very good. It means you have at least an average chip. If it will boot at 4.6 GHz and is stable there, then you may have an above average chip. The best chips will be able to do 4.8 GHz stable at 1.25 V. Our sample did 4.8 GHz, but at 1.3 V and on a custom water loop. Using 1.3 V will likely put a chip out of the air cooling / AIO water cooling thermal envelope. Temperatures in all of these scenarios, from the dog 4.3 GHz chips up to the good 4.8 GHz chips, will always be in the ~90°C range. That’s just the nature of Haswell. With the VRM on-die, think of Haswell as Ivy Bridge plus 10° C.

I have no comment on how good is your chip bro since I have never played with a 4570K before.
So far having some 4770K average chip is 4.5GHz @ 1.25v LinX stable. A golden CPU is doing as low as 1.2v at the same frequency.
Try playing with Load-line calibration in Digi+VRM option. It will control the way your CPU's idle/load vCore.

1) High performance RAM doesn't help CPU overclocking. Just that the higher RAM speed, the more stress the integrated memory controller (IMC) will get hence the more voltages you will have to pump to the processor to stabilize it.

2) The lower the temperature, the lower the vCore needed hence overclock ability is improved.

Get a better cooler bro for better overclocking. Stock cooler won't go that far 

Which cooler?  Last time my cpu stopped working completely for good.So now it is open air (no cover). Pity because the cover is fancy type.