Dual SATA-II Interface Card question and NAS question

[RockPro64Newbie]

newbie setup and usage questions. thanks humbly for assistance and guidance!

1)  Do I use "ROCKPro64 Power Cable for dual SATA Drives" to connect disk to "ROCKPro64 PCI-e to Dual SATA-II Interface Card"?

2) I assume the RockPro64 can only use qty 1 "ROCKPro64 PCI-e to Dual SATA-II Interface Card"? or can I use 2 cards instead of using 1 "NVMe SSD Interface Card"?
I have several sata III ssd drives new


3) Can I load OpenmediaVault and use as NAS (as well as use as a workstation) at the same time?
  I would use office software (word, spreadsheet, email, browser}
  
 Or does openmediavault/nas require full system attention?

Thanks!