To me ... sounds like you building your first computer
and you have lack of knowledge about how to do it , what supports what Read your motherboard description on the manufacturer website :
PRIME H270-PLUS/CSM
If you doing that , you going to find out , the only mem supported by your motherboard is DDR4
From HERE you can downlad the PRIME_H270-PLUS_MemoryQVL list
If you are going to be using 3x Vega 64 for mining and planning to add more GPUs later. " make sure you have at least 4GB of system memory
but in your case 8GB would be much better choice Ya it's been close to 15yrs since I build my last PC so am a bit Rusty.
Thanks for the link and advice. I'll stick with 8GB for this build.
Also if you can had Solid State Drive much better for computer or mining rig..
Also always check your PSU if you are planning to increase your GPU in the future watch out for watts.