i5 6400 OR i5 6402p considering below points!

[Guyinslowmo]

https://ark.intel.com/compare/93277,88185


Sorry as I can see this question was asked a multiple times but I do not get the info that I need.
I am bit confused in selecting between i5 6400 , i5 6402p. price difference isn't a matter for me if I select only from these two. & don't suggest me a different CPU as I can't get them.

I am going to build a new pc with one of the above CPUs.
Motherboard : MSI B150 PC MATE
GPU: GTX 1050ti
Ram : kingston hyperx fury 2133mhz ( let me know if this is a bad choice.I have GSKILL with CLS15 and A-DATA with CLS16 in option)


So

1) What's difference in smartcache and cache?

2) Will having lower iGPU make 6402p a bit slower in gaming even though I am using a descrete GPU.

Tell me straight if it helps me to choose.I don't mind bad words.

 

[Obakasama]

Side by side comparison from Intel's own data. If you scroll down to the cache and click it, the answer to what smart cache is also answered.

If you are using a discrete graphics card the integrated graphics is disabled by default, so it doesn't matter what the integrated graphics is.