How to determine which RAM is suitable for a PC?

Question

Iron

By what parameters should you choose a RAM?
I downloaded cpu-z
I have ddr3
The memory frequency is 794 (current)
In the frequency controller, it jumps from 794 to 3000
11 11 11 28 clock

How to find out how much RAM my percent and mainland support?
And do I need to watch the frequency for the operative there?
Or can I take new 4 boards with 1600 frequency and insert, and remove those 2?
As I read, it seems that if the frequency is higher and the clock is lower, then the RAM works faster.

Processor i7 4770 and motherboard B85M-G

I found these to choose from, but for some reason everywhere. where the timing is less and the frequency is less
So which is better, higher frequency or lower timing?
AMD Radeon R3 Value - DDR3, 8 GBx1 pcs, 1333 MHz, PC10600, 9-9-9-24
AMD Radeon R5 Entertainment - DDR3, 8 GBx1 pcs, 1600 MHz, PC12800,
11-11-11-28 11-11-11-28 (set immediately 2x8)

Answer 1

Any 1333
Radeon RAM DO NOT TAKE!!!
Take a kingston

Answer 2

definitely not a radeon