Dell R650 - Compatibility of different storage capacity for RAM memory

Hello, 

I have Dell R650 server with 12 slots x 16GB RAM for current setup and dual processor. The part number of originally installed RAM chip is HMA82GR7DJR8N-XN and details are under the link below: 

https://www.serversupply.com/MEMORY/PC4-25600/16GB/HYNIX/HMA82GR7DJR8N-XN_335988.htm

I'd like to extend RAM memory capacity and install RAM chips with 32GB or 64GB size in empty slots. 

Option no 1 - 4x32GB RAM chips - part number HMAA4GR7AJR8N-XN. 

Difference in respect to original RAM chip: 

- storage capacity - 32 GB

https://www.serversupply.com/MEMORY/PC4-25600/32GB/HYNIX/HMAA4GR7AJR8N-XN_337083.htm

Option no 2 - 2x64GB RAM chips - part number HMAA8GR7CJR4N-XN. 

https://www.serversupply.com/MEMORY/PC4-25600/64GB/HYNIX/HMAA8GR7CJR4N-XN_345991.htm

Difference in respect to original RAM chip: 

- storage capacity - 64 GB

- Rank Features: 2rx4

Please advise whether mixing of original 16GB RAM chips with 32GB or 64GB size is allowed ?

Does different rank feature for installed RAM chips affect the memory compatibility ?       

Is it enough to install only two 64G RAM chips for option 2 ? The server is equipped for 2 processors.   

Regards, 

Michal