Desktop Hardware and Upgrade Questions

Good day!
I WILL BE VERY GRATEFUL FOR YOUR HELP, SUPPORT AND ADVICE !!!
I have an HP 4CZ68EA computer, Motherboard-HP-8434 (AM4).
Computer processor - AMD Ryzen 3 PRO 2200G with VEGA 8 Graphics. AMD Radeon (tm) Vega 8 Graphics video adapter. No instructions for the computer.
In the characteristics of the computer it is written that 3.42Gb of RAM from 4Gb is available, since the built-in video card is installed. System type-64 bit operation. system, X64 processor. On the motherboard there are two slots for the establishment of RAM.
I want to increase the RAM from 4GB to 16GB.
I saw RAM in the store:
-8GB Transcend JM2666HLB-8G (you need to buy two identical modules individually 8GB x2)
-G.Skill Value 2x8GB DDR4 2666Mhz CL19Kit (everything goes in one set)
-Kingston KCP426NS8 / 8 (you need to buy two identical modules individually 8GB x2)

1, What do you think is better to buy a ready-made set of two modules for my computer or buy two identical modules individually 8GB x2?

2, What memory is better to buy for my computer:
-8GB Transcend JM2666HLB-8G (you need to buy two identical modules individually 8GB x2)
-G.Skill Value 2x8GB DDR4 2666Mhz CL19Kit (everything comes in one set) Model-F4-2666C19D-16GNT
-Kingston KCP426NS8 / 8 (you need to buy two identical modules individually 8GB x2)

3,Does Memory RAM-G. Skill's memory have a non-standard supply voltage?

4, What kind of memory do you personally recommend installing with two modules on my computer :
HP 4CZ68EA computer, Motherboard-HP-8434 (AM4).
Computer processor - AMD Ryzen 3 PRO 2200G with VEGA 8 Graphics?

5, Is there a site that determines the compatibility of RAM with the processor, motherboard and the computer itself before buying RAM?

6, I now have 4 GB of RAM, of which 05, GB is taken by the integrated video card. Will I be able to feel the difference in the increase in productivity and in another improvement in the work of the computer with an increase in RAM from 4 GB to 16 GB?

THANK YOU MUCH FOR YOUR HELP, SUPPORT AND ADVICE !!!
THANK YOU VERY MUCH FOR YOUR HELP AND SUPPORT !!!
BEST REGARDS, Grigoriy.